Power scaling

ABSTRACT

Disclosed are systems and methods for measuring and calculating parameters to control and monitor a power transfer in an implanted medical device, including operating the device in a plurality of scalable power modes and/or coupling modes. The system may shift between or among power and/or coupling modes based on input such as data received over system communication lines, programmable timers, or electrical loading information. The system may also shift between or among power and/or coupling modes based on calculated amounts of coupling, levels of detected heat flux, and/or amounts of estimated temperature changes.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims the benefit under 35 U.S.C. §119(e) toU.S. Provisional Patent Application No. 62/029,333 filed on Jul. 25,2014, U.S. Provisional Patent Application No. 62/104,430 filed on Jan.16, 2015, U.S. Provisional Patent Application No. 62/104,444 filed onJan. 16, 2015, and U.S. Provisional Patent Application No. 62/147,416filed on Apr. 14, 2015. The entire contents of each of thesepreviously-flied provisional applications are incorporated by referenceas if fully disclosed herein.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

This invention was made with Government support under one or more SmallBusiness Innovation Research (SBIR) grants awarded by the Public HealthService (PHS). The Government has certain rights in the invention.

TECHNICAL FIELD

The technology described herein relates to systems and methods formeasuring and calculating parameters to control and monitor a powertransfer in an implanted medical device including operating the systemin a plurality of scalable power and/or coupling modes.

BACKGROUND

Currently, there is a need to deliver electric power to implantedmedical devices such as artificial hearts and ventricle assist devices.It is possible to deliver power non-invasively through electromagneticenergy transmitted through the skin. However, problems can arise relatedto the implanted secondary, which receives power from the externalprimary. In one respect, the system can operate over limited powerand/or coupling ranges. Here, the resonant network that transfers powerfrom the primary to the secondary is typically designed both for startupconditions that momentarily require a high power and for normaloperating conditions that require less power. Operating the system inboth of these conditions using the same resonant network can limit thepower and coupling ranges that are available to the system. In anotherrespect, the secondary can heat-up and injure the subject due toinadvertent non-optimal coupling, including possibly over-coupling orunder-coupling, between the primary and the secondary. Because thesecondary is implanted and thus relatively inaccessible, a problem canarise and cause injury before the user or the system is aware of theproblem. Prior art systems fail to provide mechanisms for addressingthese and other issues that concern transfer of electromagnetic energyto implanted medical devices. These and other deficiencies of the priorart are addressed herein.

SUMMARY

Present embodiments are directed to measuring and calculating parametersto control and monitor a power transfer in an implanted medical device,including operating the device in a plurality of scalable power modesand/or coupling modes. The medical device may be implanted in a subjectand can include an artificial heart or ventricle assist device. In onerespect, the system shifts between or among power and/or coupling modesbased on input such as data received over system communication lines,programmable timers, or electrical loading information. In anotherrespect, the system measures parameters and uses the parameters tocalculate a coupling coefficient for coils that transfer power betweenan external primary and an implanted secondary. The system may then usethe calculated coupling coefficient to estimate temperature changes orheat flux being generated in the system. The system may then shiftbetween or among power and/or coupling modes based on the amount ofcoupling, the level of heat flux detected, or the amount of estimatedtemperature changes.

In one aspect, the present disclosure is directed to a method ofmonitoring and controlling power transfer between a primary and asecondary of a transcutaneous energy transfer system used in animplantable medical device, including operating the transcutaneousenergy transfer system in a first power mode, the first power mode beingone of a plurality of scalable power modes, determining if thetranscutaneous energy transfer system is to be switched to a secondpower mode, the second power mode being one of the plurality of scalablepower modes, and switching from the first power mode to the second powermode by controlling power transfer between the primary and secondary.

In some implementations, the primary includes a power transmittingsystem including a primary coil.

In some implementations, the secondary includes a power receiving systemincluding a secondary coil.

In some implementations, the scalable power modes include a set of powerdelivery ranges defined from a low power range to a high power range.

In some implementations, the set of power delivery ranges includes atleast one intermediate power delivery range between the low power rangeand the high power range.

In some implementations, determining if the transcutaneous energytransfer system is to be switched includes determining if a request tocomplete an initial power up sequence is received.

In some implementations, determining if the transcutaneous energytransfer system is to be switched includes determining if a request toverify the correct secondary is received.

In some implementations, determining if the transcutaneous energytransfer system is to be switched includes determining if a request forincreased or decreased power is received

In some implementations, determining if the transcutaneous energytransfer system is to be switched includes determining if a request toenter a fault mode is received.

In some implementations, determining if the transcutaneous energytransfer system is to be switched includes determining if apredetermined time has elapsed since power up.

In some implementations, determining if the transcutaneous energytransfer system is to be switched includes determining if apredetermined time has elapsed since a fault condition was detected.

In some implementations, determining if the transcutaneous energytransfer system is to be switched includes determining if apredetermined time has elapsed since a change in a coupling coefficientoccurred.

In some implementations, determining if the transcutaneous energytransfer system is to be switched includes determining if a faultcondition is detected.

In some implementations, the fault condition includes excess currentbeing drawn by the secondary.

In some implementations, determining if the transcutaneous energytransfer system is to be switched includes determining if a change inthe coupling coefficient is detected.

In some implementations, determining if the transcutaneous energytransfer system is to be switched includes determining if a load changeis detected.

In some implementations, the load change is indicated in by a change inthe duty cycle measured at the primary.

In some implementations, controlling power transfer between the primaryand secondary includes changing the power mode by an operation of avariable transformer on the primary side.

In some implementations, the variable transformer has a plurality ofdiscrete states each corresponding to one of the scalable power modes.

In some implementations, controlling power transfer between the primaryand secondary includes changing the power mode by varying input powerwith subharmonics of drive frequency.

In some implementations, the input power has a plurality of subharmonicstates each corresponding to one of the scalable power modes.

In some implementations, controlling the power transfer between theprimary and secondary includes changing the power mode by an operationof a variable voltage regulator on the primary side.

In some implementations, the variable voltage regulator has a pluralityof discrete states each corresponding to one of the scalable powermodes.

In some implementations, controlling the power transfer between theprimary and secondary includes changing the power mode by an operationof a phase shifted bridge controller on the primary side.

In some implementations, the phase shifted bridge controller isconfigured for a plurality of phase shifts each corresponding to one ofthe scalable power modes.

In another aspect, the present disclosure is directed to a transformerfor a transcutaneous energy transmission device, the transformerincluding a cored transformer having a primary side and a secondaryside, the primary side configured to connect to a power supply, avariable transformer section having a first end and a second end, thefirst end connected to the secondary side of the cored transformer, anda coreless transformer having a primary side and a secondary side, theprimary side connected to the second end of the variable transformersection, the secondary side configured to be implanted within a subjectsuch that the skin of the subject is disposed between the primary andsecondary sides of the coreless transformer.

In some implementations, the variable transformer section furtherincludes a terminal winding configured as the primary winding of thecoreless transformer, a first transformer leg having a transformerwinding connected to the second side of cored transformer, and a secondtransformer leg having a transformer winding connected to the secondside of the cored transformer.

In some implementations, the first transformer leg and the secondtransformer leg are arranged in parallel.

In some implementations, the first transformer leg includes capacitorconnected in series with the transformer winding connected to thesecondary side of cored transformer and the second transformer legincludes capacitor connected in series with the transformer windingconnected to the secondary side of cored transformer.

In some implementations, the first transformer leg includes a switchthat, when opened, disconnects the first leg from the terminal winding,and the second transformer leg includes a switch that, when opened,disconnects the second leg from the terminal winding.

In some implementations, the switches of the first and secondtransformer legs are connected to a controller that opens and closes theswitches to switch the transcutaneous energy transmission device betweenat least a high power mode and a low power mode.

In another aspect, the present disclosure is directed to a method ofextending coupling range during power transfer between a primary and asecondary of a transcutaneous energy transfer system for an implantedmedical device, including operating the transcutaneous energy transfersystem in a first coupling mode, the first coupling mode being one of aplurality of coupling modes, determining if the transcutaneous energytransfer system is to be switched to a second coupling mode, the secondcoupling mode being one of the plurality of coupling modes, andswitching from the first coupling mode to the second coupling mode byincreasing or decreasing the power transfer between the primary and thesecondary as the coupling changes.

In some implementations, the primary includes a power transmittingsystem including a primary coil.

In some implementations, the secondary includes a power receiving systemincluding a secondary coil.

In some implementations, the scalable coupling modes includes a set ofcoupling ranges defined from a low coupling range to a high couplingrange.

In some implementations, the set of coupling ranges includes at leastone intermediate coupling range between the low coupling range and thehigh coupling range.

In some implementations, determining if the transcutaneous energytransfer system is to be switched includes detecting, on the primaryside, the coupling between the primary and the secondary.

In some implementations, controlling power transfer between the primaryand secondary includes changing the amount of delivered power by anoperation of a variable transformer on the primary side.

In some implementations, the variable transformer has a plurality ofdiscrete states each corresponding to one of the coupling modes.

In some implementations, controlling power transfer between the primaryand secondary includes changing the amount of delivered power by varyinginput power with subharmonics of drive frequency.

In some implementations, the input power has a plurality of subharmonicstates each corresponding to one of the coupling modes.

In some implementations, controlling the power transfer between theprimary and secondary includes changing the power mode by an operationof a variable voltage regulator on the primary side.

In some implementations, the variable voltage regulator has a pluralityof discrete states each corresponding to one of the coupling modes.

In some implementations, controlling the power transfer between theprimary and secondary includes changing the power mode by an operationof a phase shifted bridge controller on the primary side.

In some implementations, the phase shifted bridge controller isconfigured for a plurality of phase shifts each corresponding to one ofthe coupling modes.

In some implementations, switching between a low coupling mode and ahigh coupling mode supports placement assistance of the primary coilsuch that a low coupling mode is used to indicate the placement of thedevice is not optimal and a high coupling mode is used to indicate amore optimal placement.

In another aspect, the present disclosure is directed to a method ofoperating a transcutaneous energy transfer system for an implantedmedical device, including transferring power from a primary to animplanted secondary in the transcutaneous energy transfer system,determining a placement of a primary coil in relation to a location of asecondary coil, operating the transcutaneous energy transfer system in alow coupling mode if the placement of the primary coil is non-optimal,and operating the transcutaneous energy transfer system in a highcoupling mode if the placement of the primary coil is more optimal.

In some implementations, the method of operating a transcutaneous energytransfer system further includes operating the transcutaneous energytransfer system in an intermediate coupling mode between the lowcoupling mode and the high coupling mode if indicated by the placementof the primary coil.

In some implementations, the method of operating a transcutaneous energytransfer system further includes switching between the first couplingmode to the second coupling mode by increasing or decreasing the powertransfer between the primary and the secondary as the coupling changes.

In some implementations, controlling power transfer between the primaryand secondary includes changing the amount of delivered power by anoperation of a variable transformer on the primary side.

In some implementations, the variable transformer has a plurality ofdiscrete states each corresponding to one of the coupling modes.

In some implementations, controlling power transfer between the primaryand secondary includes changing the amount of delivered power by varyinginput power with subharmonics of drive frequency.

In some implementations, the input power has a plurality of subharmonicstates each corresponding to one of the coupling modes.

In some implementations, controlling the power transfer between theprimary and secondary includes changing the power mode by an operationof a variable voltage regulator on the primary side.

In some implementations, the variable voltage regulator has a pluralityof discrete states each corresponding to one of the coupling modes.

In some implementations, controlling the power transfer between theprimary and secondary includes changing the power mode by an operationof a phase shifted bridge controller on the primary side.

In some implementations, the phase shifted bridge controller isconfigured for a plurality of phase shifts each corresponding to one ofthe coupling modes.

In another aspect, the present disclosure is directed to a transformerfor a transcutaneous energy transmission device, the transformer,including a cored transformer having a primary side and a secondaryside, the primary side configured to connect to a power supply, avariable transformer section having a first end and a second end, thefirst end connected to the secondary side of the cored transformer, anda coreless transformer having a primary side and a secondary side, theprimary side connected to the second end of the variable transformersection, the secondary side configured to be implanted within a subjectsuch that the skin of the subject is disposed between the primary andsecondary sides of the coreless transformer.

In some implementations, the variable transformer section furtherincludes a terminal winding configured as the primary winding of thecoreless transformer, a first transformer leg having a transformerwinding connected to the second side of cored transformer, and a secondtransformer leg having a transformer winding connected to the secondside of the cored transformer.

In some implementations, the first transformer leg and the secondtransformer leg are arranged in parallel.

In some implementations, the first transformer leg includes capacitorconnected in series with the transformer winding connected to thesecondary side of cored transformer, and the second transformer legincludes capacitor connected in series with the transformer windingconnected to the secondary side of cored transformer.

In some implementations, the first transformer leg includes a switchthat, when opened, disconnects the first leg from the terminal winding,and the second transformer leg includes a switch that, when opened,disconnects the second leg from the terminal winding.

In some implementations, the switches of the first and secondtransformer legs are connected to a controller that opens and closes theswitches to switch the transcutaneous energy transmission device betweenat least a high coupling mode and a low coupling mode.

In another aspect, the present disclosure is directed to a portableexternal device for a mechanical circulation support (MCS) systemincluding a housing, a battery removably connected to the housing, andpower module arranged within the housing, powered by the battery andconfigured to wirelessly transfer electric power across a skin boundaryto an implantable pump via a transcutaneous energy transfer system.

In some implementations, the power module is configured to operate thetranscutaneous energy transfer system in a first power mode, the firstpower mode being one of a plurality of scalable power modes, determineif the transcutaneous energy transfer system is to be switched to asecond power mode, the second power mode being one of the plurality ofscalable power modes, and switch from the first power mode to the secondpower mode by controlling power transfer between the primary andsecondary.

In some implementations, the primary includes a power transmittingsystem including a primary coil.

In some implementations, the secondary includes a power receiving systemincluding a secondary coil.

In some implementations, the scalable power modes includes a set ofpower delivery ranges defined from a low power range to a high powerrange.

In some implementations, the set of power delivery ranges includes atleast one intermediate power delivery range between the low power rangeand the high power range.

In some implementations, determining if the transcutaneous energytransfer system is to be switched includes determining if a request tocomplete an initial power up sequence is received.

In some implementations, determining if the transcutaneous energytransfer system is to be switched includes determining if a request toverify the correct secondary is received.

In some implementations, determining if the transcutaneous energytransfer system is to be switched includes determining if a request forincreased or decreased power is received.

In some implementations, determining if the transcutaneous energytransfer system is to be switched includes determining if a request toenter a fault mode is received.

In some implementations, determining if the transcutaneous energytransfer system is to be switched includes determining if apredetermined time has elapsed since power up.

In some implementations, determining if the transcutaneous energytransfer system is to be switched includes determining if apredetermined time has elapsed since a fault condition was detected.

In some implementations, determining if the transcutaneous energytransfer system is to be switched includes determining if apredetermined time has elapsed since a change in a coupling coefficientoccurred.

In some implementations, determining if the transcutaneous energytransfer system is to be switched includes determining if a faultcondition is detected.

In some implementations, the fault condition includes excess currentbeing drawn by the secondary.

In some implementations, determining if the transcutaneous energytransfer system is to be switched includes determining if a change inthe coupling coefficient is detected.

In some implementations, determining if the transcutaneous energytransfer system is to be switched includes determining if a load changeis detected.

In some implementations, the load change is indicated in by a change inthe duty cycle measured at the primary.

In some implementations, controlling power transfer between the primaryand secondary includes changing the power mode by an operation of avariable transformer on the primary side.

In some implementations, the variable transformer has a plurality ofdiscrete states each corresponding to one of the scalable power modes.

In some implementations, controlling power transfer between the primaryand secondary includes changing the power mode by varying input powerwith subharmonics of drive frequency.

In some implementations, the input power has a plurality of subharmonicstates each corresponding to one of the scalable power modes.

In some implementations, controlling the power transfer between theprimary and secondary includes changing the power mode by an operationof a variable voltage regulator on the primary side.

In some implementations, the variable voltage regulator has a pluralityof discrete states each corresponding to one of the scalable powermodes.

In some implementations, controlling the power transfer between theprimary and secondary includes changing the power mode by an operationof a phase shifted bridge controller on the primary side.

In some implementations, the phase shifted bridge controller isconfigured for a plurality of phase shifts each corresponding to one ofthe scalable power modes.

In some implementations, the power module of the portable externaldevice further includes a cored transformer having a primary side and asecondary side, the primary side configured to connect to the battery, avariable transformer section having a first end and a second end, thefirst end connected to the secondary side of the cored transformer, anda coreless transformer having a primary side and a secondary side, theprimary side connected to the second end of the variable transformersection, the secondary side configured to be implanted within a subjectsuch that the skin of the subject is disposed between the primary andsecondary sides of the coreless transformer.

In some implementations, the variable transformer section furtherincludes a terminal winding configured as the primary winding of thecoreless transformer, a first transformer leg having a transformerwinding connected to the second side of cored transformer, and a secondtransformer leg having a transformer winding connected to the secondside of the cored transformer.

In some implementations, the first transformer leg and the secondtransformer leg are arranged in parallel.

In some implementations, the first transformer leg includes capacitorconnected in series with the transformer winding connected to thesecondary side of cored transformer, and the second transformer legincludes capacitor connected in series with the transformer windingconnected to the secondary side of cored transformer.

In some implementations, the first transformer leg includes a switchthat, when opened, disconnects the first leg from the terminal winding,and the second transformer leg includes a switch that, when opened,disconnects the second leg from the terminal winding.

In some implementations, the switches of the first and secondtransformer legs are connected to a controller that opens and closes theswitches to switch the transcutaneous energy transmission device betweenat least a high power mode and a low power mode.

In some implementations, the battery, when connected to the housing,forms an integral portion of the housing and wherein the batteryincludes an energy dense battery.

In some implementations, the battery includes a rechargeable batteryconfigured to operate without recharge for a period of time in a rangefrom approximately 4 hours to approximately 12 hours.

In some implementations, the rechargeable battery is configured tooperate without recharge for a period of time approximately equal to 8hours.

In some implementations, the housing includes a width in a range fromapproximately 60 millimeters to approximately 90 millimeters, a lengthin a range from approximately 100 millimeters to approximately 140millimeters, and a depth in a range from approximately 20 millimeters toapproximately 40 millimeters.

In some implementations, the housing includes a volume in a range fromapproximately 120 centimeters cubed to approximately 504 centimeterscubed.

In some implementations, the portable external device includes a weightin a range from approximately 0.25 kilograms to approximately 1.0kilograms.

In some implementations, the portable external device further includes alatch configured to release the battery for removal from the housing,wherein the latch is configured to be actuated to release the batteryfor removal from the housing by at least two independent motions.

In some implementations, the latch includes two push buttons, each ofwhich is biased into a locked position that inhibits removal of thebattery from the housing, and both of which are configured to be pushedinto an unlocked position simultaneously to release the battery forremoval from the housing.

In some implementations, the two push buttons are arranged on opposingsides of the housing such that the two buttons are configured to bepushed in approximately opposite directions to one another.

In some implementations, the latch includes a channel and a post biasedinto a locked position toward a first end of the channel that inhibitsremoval of the battery from the housing, and wherein the post isconfigured to be pushed in at least two directions toward a second endof the channel into an unlocked position to release the battery forremoval from the housing.

In some implementations, each of the battery and the power module isconfigured to power the implantable pump.

In some implementations, the energy dense battery includes a lithium-ion(Li-ion), nickel-metal hydride (NiMH), or nickel-cadmium (NiCd)rechargeable battery.

In some implementations, the energy dense battery includes an energydensity in a range from approximately 455 watt-hours per liter toapproximately 600 watt-hours per liter.

In some implementations, the power dense second battery includes a powerdensity in a range from approximately 700 watts per liter toapproximately 6 kilowatts per liter.

In some implementations, the portable external device further includesat least one piezoelectric speaker controlled by the power module toemit one or more audible sounds.

In some implementations, the portable external device further includes afirst telemetry module configured to communicate information between theportable external device and one or more other devices according to afirst wireless communication technique.

In some implementations, the portable external device further includes asecond telemetry module configured to communicate information betweenthe portable external device and one or more other devices according toa second wireless communication technique.

In some implementations, the first wireless communication technique isdifferent than the second wireless communication technique.

In some implementations, the portable external device further includes auser interface including a capacitive sensor configured to receive userinput.

In some implementations, the portable external device further includes adepression in which the capacitive sensor is arranged.

In some implementations, power consumed by the power module is in arange from approximately 0.25 to approximately 1.25 watts.

This Summary is provided to introduce a selection of concepts in asimplified form that are further described below in the DetailedDescription. This Summary is not intended to identify key features oressential features of the claimed subject matter, nor is it intended tobe used to limit the scope of the claimed subject matter. A moreextensive presentation of features, details, utilities, and advantagesof the present invention as defined in the claims is provided in thefollowing written description of various embodiments of the inventionand illustrated in the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a conceptual diagram illustrating an example left ventricularassist device (LVAD) including a portable external control and powersource module.

FIGS. 2A-E are a number of plan and elevation views illustrating anexample of the control and power source module of FIG. 1.

FIG. 3 is an exploded view of the example control and power sourcemodule of FIGS. 2A-2E.

FIGS. 4A and 4B are perspective views of the battery release latch ofthe example control and power source module of FIGS. 2A-3.

FIGS. 4C-4H illustrate a number of alternative battery release latchmechanisms that may be employed in conjunction with control and powersource modules according to this disclosure.

FIG. 5 is functional block diagram illustrating an example control andpower source module according to this disclosure.

FIG. 6 is a state diagram representing a process by which the status ofpower sources of the control and power source module of FIG. 5 may becommunicated to a user.

FIGS. 7A-10B illustrate a number of functions associated with elementsof an example user interface of the control and power source module ofFIG. 5.

FIGS. 11A-11J (“FIG. 11”) are circuit diagrams illustrating circuitry ofan example of the power junction of the control and power source moduleof FIG. 5.

FIGS. 12A-12F (“FIG. 12”) are circuit diagrams illustrating circuitry ofan example of the charger of the control and power source module of FIG.5.

FIGS. 13A and 13B illustrate another battery release latch mechanismthat may be employed in conjunction with control and power sourcemodules according to this disclosure.

FIGS. 14A-14D illustrate two other battery release latch mechanisms thatmay be employed in conjunction with control and power source modulesaccording to this disclosure.

FIG. 15 is a block diagram of a wireless power transfer system inaccordance with embodiments discussed herein.

FIG. 16A is a circuit diagram for certain components of the system shownin FIG. 15.

FIG. 16B is circuit diagram for certain components of the system shownin FIG. 15 that includes a variable transformer topology having twotransformer legs.

FIG. 16C is circuit diagram for certain components of the system shownin FIG. 15 that includes a variable transformer topology having anarbitrary number of transformer legs.

FIGS. 17A and 17B are schematic illustrations of the internal andexternal coils shown in FIG. 15.

FIG. 18A is a circuit diagram that shows one implementation of theinverter shown in FIG. 15.

FIG. 18B is a circuit diagram that shows one implementation of theinverter shown in FIG. 15 that includes a variable transformer topologyhaving two transformer legs.

FIG. 18C is a circuit diagram that shows one implementation of theinverter shown in FIG. 15 that includes a variable transformer topologyhaving an arbitrary number of transformer legs.

FIG. 18D is a schematic diagram of an implementation of the system ofFIG. 15 where the external resonant network of FIG. 15 is connecteddirectly to the inverter.

FIG. 18E is a schematic diagram of an implementation of the system ofFIG. 15 where the external resonant network is connected to the inverterthrough a variable transformer section.

FIG. 18F is a schematic diagram of an implementation of the system ofFIG. 15 where that includes a variable voltage regulator.

FIG. 19 is a graph that illustrates different subharmonics of powertransmission frequency for a system in accordance with embodimentsdiscussed herein.

FIG. 20 is a graph that illustrates the operation of a system embodimentthat implements two coupling modes.

FIG. 21 is an illustration of waveform traces for signals that arepresent in the system of FIG. 15 as power is transferred between theexternal assembly and the internal assembly.

FIG. 22 is a collection of coupling coefficient data sets for the systemshown in FIG. 15.

FIG. 23 is graphical illustration of safety level data acquired in anempirical study.

FIG. 24 is a flow chart that illustrates a method of shifting between oramong scalable power modes in accordance with embodiments discussedherein.

FIG. 25 is a flow chart that illustrates controller operations thatprovide for determining whether or not a system should shift based oninput received from communication channels.

FIG. 26 is a flow chart that illustrates controller operations thatprovide for determining whether or not a system should shift power modesbased on system timers.

FIG. 27 is a flow chart that illustrates controller operations thatprovide for determining whether or not a system should shift power modesbased on calculated coupling amounts.

FIG. 28 is a flow chart that illustrates controller operations thatprovide for determining whether or not a system should shift power modesbased on whether or not a fault condition is detected.

FIG. 29 is a flow chart that illustrates controller operations thatprovide for determining whether or not a system should shift power modesbased on loading conditions that are present in the secondary.

FIG. 30 is a flow chart that illustrates a method of shifting between oramong scalable coupling modes in accordance with embodiments discussedherein.

FIG. 31 is a flow chart that illustrates controller operations thatprovide for determining whether or not a system should shift couplingmodes based on calculated coupling amounts.

FIG. 32 is a flow chart that illustrates controller operations thatprovide for determining whether or not a system should shift couplingmodes based on the placement of the primary coil in relation to thesecondary coil.

FIG. 33 is a flow chart that illustrates a method of a calculating acoupling coefficient in accordance with embodiments discussed herein.

FIG. 34 is a flow chart that illustrates a method of estimating asecondary coil heat flux in accordance with embodiments discussedherein.

FIG. 35 is a flow chart that illustrates a method of estimating asecondary coil temperature in accordance with embodiments discussedherein.

FIG. 36 is a flow chart that illustrates a method of estimating aprimary coil heat flux in accordance with embodiments discussed herein.

FIG. 37 is a flow chart that illustrates a method of estimating aprimary coil heat temperature in accordance with embodiments discussedherein.

DETAILED DESCRIPTION

Present embodiments are directed to measuring and calculating parametersto control and monitor a power transfer in an implanted medical device,including operating the device in a plurality of scalable power modesand/or coupling modes. The medical device may be implanted in a subjectand can include an artificial heart or ventricle assist device. In onerespect, the system shifts between or among power and/or coupling modesbased on input such as data received over system communication lines,programmable timers, or electrical loading information. In anotherrespect, the system measures parameters and uses the parameters tocalculate a coupling coefficient for coils that transfer power betweenan external primary and an implanted secondary. The system may then usethe calculated coupling coefficient to estimate temperature changes orheat flux being generated in the system. The system may then shiftbetween or among power and/or coupling modes based on the amount ofcoupling, the level of heat flux detected, or the amount of estimatedtemperature changes.

In accordance with various embodiments, a determination may be made toshift the system between or among power and/or coupling modes based on arequest to complete an initial power-up sequence, a request to verifythe correct secondary, a request for increased or decreased power,and/or a request to enter a fault mode. In other embodiments, the systemmay shift between or among power and/or coupling modes when apredetermined time has elapsed since power-up, a predetermined time haselapsed since a fault condition was detected, and/or a predeterminedtime has elapsed since a change in a coupling coefficient occurred. Thesystem may also shift between or among power and/or coupling modes if afault condition is detected, if a change in the coupling coefficient isdetected, and/or if a load change is detected.

FIG. 1 is a conceptual diagram illustrating an example left ventricularassist device (LVAD) 10 including portable control and power sourcemodule 12 that is configured to provide electrical power to an implantedpump controller 21 and implanted pump 14 through a wireless powertransfer system 11. Control and power source module 12 includes housing22, an optional internal battery (see FIGS. 3 and 5), and removablebattery 24 shown in FIG. 1. Control and power source module 12 alsoincludes connector 26 and user interface 50. User interface 50 includesdisplay screen 52 and input buttons 54, as well as a number of otherelements described below with reference to FIG. 2B.

The wireless power transfer system 11 includes an external resonantnetwork 15 that is disposed on the exterior of the patient 22 and aninternal resonant network 17 that is implanted within the patient 22.The external resonant network 15 connects to the control and powersource module 12 through an external cable 19. The internal resonantnetwork 17 connects to an internal controller module 21 through aninternal cable 18. The internal controller module 21 is generallyconfigured to manage a power transfer that occurs across the external 15and internal 17 resonant networks and to provide power and pump controlto the implanted pump 14. In some implementations, the implant pumpcontroller module 21 includes a battery that provides power to theimplanted pump 14 when the power is not available through from acrossthe external 15 and internal 17 resonant networks. In thisimplementation, the internal battery associated with the control andpower source module 12 may be omitted and battery charging support isincluded within the implant pump controller. The operation on the TETScomponent 11 is described in greater detail below in connection withFIGS. 15-30.

As described in greater detail in the following examples, control andpower source module 12 is a portable external device for a mechanicalcirculation support system that includes a controller for transferringpower to implanted pump controller 21 and implanted pump 12, which ispowered by a power source integral with the controller. The power sourceof example control and power source module 12 includes removable battery24, which is removably connected to housing 22 of the control and powersource module, and an internal back-up battery (see FIGS. 3 and 5)arranged within the housing. Control and power source module 12 is sizedto accommodate a variety of wearable configurations for patient 20,including, e.g., being worn on a belt wrapped around the waist ofpatient 20 in FIG. 1.

The external 15 and internal 17 resonant networks connect control andpower source module 12 and implanted pump controller 21 to communicatepower and other signals between the external module and the implantedpump controller. In the example of FIG. 1, cable 19 connects to controland power source module 12 via connector 26. Cable 19 may be fabricatedin a variety of lengths and may be employed to improve the flexibilityof wearing control and power source module 12 on the body of patient 20.In one example, cable 19 may be itself extendable such that the cablecan assume a number of different lengths. For example, cable 19 may becoiled such that stretching and unwinding the coiled cable extensionwill cause it to assume a number of different lengths. In anotherexample, control and power source module 12 may include a mechanism fromwhich cable 19 may be unwound and to which the extension may be rewoundto cause it to assume a number of different lengths.

Control and power source module 12 also includes control electronics(not shown in FIG. 1) configured to control operation of variouscomponents of LVAD 10 including implanted pump controller 21, removablebattery 24, the internal battery (see FIGS. 3 and 5), and user interface50. As noted above, user interface 50 includes display screen 52 andinput buttons 54. Display screen 52 may include a number of differenttypes of displays, including, e.g., a liquid crystal display (LCD), dotmatrix display, light-emitting diode (LED) display, organiclight-emitting diode (OLED) display, touch screen, or any other devicecapable of delivering to and/or accepting information from a user.Display 52 may be configured to present text and graphical informationin one or more colors. For example, display 52 may be configured todisplay the charge status of removable battery 24 and the internalbattery of control and power source module 12, as well as present alarmsto a user including instructions for taking action in response to thealarm. In an implementation where the internal battery associated withthe control and power source module 12 is omitted, the display 52 may beconfigured to display the charge status of the implanted batteryincluded within the implant pump controller 21. In one example ofcontrol and power source module 12, input buttons 54 are non-contactcapacitive sensors configured to indicate input from a user without theuser actually touching the buttons or any other part of the control andpower source module.

Pump 14 of LVAD 10 may be surgically implanted within patient 20including, e.g., in the abdominal cavity of the patient as illustratedin the example of FIG. 1. In other examples, pump 14 may be implanted inother locations within patient 20. Pump 14 is connected to heart 30 ofpatient 20 by inlet and outlet cannula 32, 34. In the example LVAD 10 ofFIG. 1, inlet cannula 32 communicates blood from left ventricle 36 (LV)of heart 30 pump 14. Outlet cannula 34 communicates blood from pump 14to aorta 38 of patient 20. Pump 14 includes a rigid housing formed fromor with a biocompatible material or coating that resists corrosion anddegradation from bodily fluids. Examples of suitable biocompatiblematerials include titanium and biologically inert polymers. Pump 14 mayinclude a variety of types of positive displacement mechanisms capableof drawing blood into and ejecting the blood out of the pump. Forexample, pump 14 may include one of a centrifugal impeller, peristaltic,electromagnetic piston, axial flow turbine pump, magnetic bearing rotarypump, pneumatic displacement pump or another positive displacementmechanism appropriate for use with implantable devices such as RVAD 10.

The implant pump controller 21 is generally configured to provide powerand control inputs to the implanted pump 14 and/or other component ofthe LVAD 10. In one respect, the implant pump controller 21 includes apower circuit and a rectifier through which the controller 21 manages apower transfer that occurs across the external 15 and internal 17resonant networks. In another respect, includes power transfercomponents through which the controller provides power to the implantedpump 14. The various components of the implant pump controller 21including the power circuit, rectifier, and power transfer componentsare described in greater detail in connection with FIGS. 15 and 16.

In the example of FIG. 1, ventricular assist system 10 is illustratedassisting left ventricle 36 (LV) of heart 30 of patient 20. However, inother examples, the techniques disclosed may be employed in other typesof mechanical circulation support (MCS) systems configurable to, e.g.,assist right ventricle 40 in a right ventricular assist device (RVAD),as well as both ventricles 36, 40 in a biventricular assist device(BiVAD). As a general matter, therefore, the source of blood for exampleVADs may be described generally as the assisted ventricle, while thedestination of the pressurized blood delivered by the control and powersource module may be designated as the arterial vessel.

Referring again to FIG. 1, each of inlet and outlet cannulas 32, 34 maybe formed from flexible tubine extending to left ventricle 36 and aorta38, respectively. Inlet and outlet cannulas 32, 34 may be attached totissue of left ventricle 36 and aorta 38, respectively, by, e.g.,sutures to establish and maintain blood flow, and may includeappropriate structure for such attachment techniques including, e.g.suture rings 42, 44. In any of the aforementioned LVAD, RVAD, or BiVADconfigurations, inlet cannula 32 is anastomosed to the assistedventricle (or ventricles), while outlet cannula 34 is anastomosed to thecorresponding assisted arterial vessel, which for left ventricularassist is typically aorta 38 and for right ventricular assist istypically pulmonary artery 46.

FIGS. 2A-E are a number of plan and elevation views illustrating anexample configuration of control and power source module 12 of FIG. 1.FIG. 2A is a front elevation view of example control and power sourcemodule 12. FIGS. 2B and 2C are left and right elevation views,respectively, of control and power source module 12. FIGS. 2D and 2E aretop and bottom plan views, respectively, control and power source module12. Control and power source module 12 includes housing 22, userinterface 50, cable port 60, external power source port 62, batteryrelease buttons 64 and 66, and removable battery bay door 68. Userinterface 50 includes display screen 52, input buttons 54, as well asmute button 70 and status indicators 72 and 74 illustrated in FIG. 2B.

Control and power source 12 includes a controller for controllingimplanted pump 12 powered by a power source integral with the controllerand is sized to accommodate a variety of wearable configurations forpatient 20, including, e.g., being worn on a belt wrapped around thewaist of the patient, as illustrated in FIG. 1. In one example, controland power source module 12, and, in particular, housing 22 is fabricatedto specific size and weight targets to maintain the module at a sizethat facilitates flexibility and convenience for patient 20. Forexample, housing 22 of control and power source module 12 may befabricated with a length, L, in a range from approximately 100millimeters to approximately 140 millimeters, a width, W, in a rangefrom approximately 60 millimeters to approximately 90 millimeters, and adepth, D, in a range from approximately 20 millimeters to approximately40 millimeters. Control and power source module 12 may also be sizedbased on a total volume of the device. For example, housing 22 ofcontrol and power source module 12 may be fabricated to include a volumein a range from approximately 120 centimeters cubed to approximately 504centimeters cubed. In one example, in addition to or in lieu of specificsize targets, control and power source module 12 may also include atarget weight. For example, control and power source module 12,including removable battery 24 and the internal battery (not shown inFIGS. 2A-E) may be fabricated to include a weight in a range fromapproximately 0.4 kilograms to approximately 0.8 kilograms.

The size and weight of control and power source module 12 may depend, atleast in part, on the components of which the device is comprised,including, e.g. housing 22, display 52, removable battery 24 and in theinternal battery, as well as the control electronics arranged within thehousing of the device. In one example, the electronics of control andpower source module 12 may include, e.g., one or more processors,memory, telemetry, charging circuitry, speakers, power managementcircuitry, and power transfer circuitry. In any event, the size andweight of the internal components of control and power source module,including, e.g., display 52, status indicators 72 and 74, and theinternal electronics of the device, may be proportional to the energyrequired to power the components. Thus, reducing the energy requirementsof the electronics of control and power source module 12 may not onlyserve to extend battery life, but may also reduce the size and weight ofthe device.

In another example, control and power source module 12 may be configuredsuch that the power consumed by the electronics of the control and powersource module is equal to a target value. For example, the electronicsof control and power source module 12 may be configured to consume powerin a range from approximately 0.25 to approximately 1.25 watts.

Example control and power source module 12 of FIGS. 2A-2E includes userinterface 50, including display screen 52, input buttons 54, mute button70 and status indicators 72 and 74. Display screen 52 may include anumber of different types of displays, and may be configured to presenttext and graphical information in one or more colors. In one example,input buttons 54 are non-contact capacitive sensors configured toindicate input from a user without the user actually touching thebuttons or any other part of the control and power source module.Although input buttons 54 may, in one example, include non-contactsensors, the buttons may be arranged in depressions 76 in housing 22provide tactile feedback to a user searching for or using the buttons toview information on display 52 and otherwise interact with control andpower source module 12. In one example, input buttons 54 may be softkeys configured to execute different functions on control and powersource module 12 based on, e.g., current functions and contextsindicated on display 52. In such examples, the current functionassociated buttons 54 operating as soft keys may be presented as labelson display 52 just above each of the buttons. In one example, inputbuttons 54 correspond to two main functions for interacting with controland power source module 12. For example, one of input buttons 54 mayfunction as a “home” button that, when activated by a user, navigates toa default screen presented on display 52 of user interface 50.Additionally, in such an example, the other one of input buttons 54 mayfunction as a “next” button that, when activated by a user, toggles tothe next screen in a series of possible screens that may be presented ondisplay 52 of user interface 50.

As illustrated in FIG. 2E, user interface 50 of control and power sourcemodule 12 also includes mute button 70 and status indicators 72 and 74.In one example, mute button 70 may be configured to, when depressed,mute audible alerts issued by speakers of control and power sourcemodule 12. Mute button 70 may, in one example, only mute alertstemporarily, for example to allow patient 20 to leave a public placewith other people that may be disturbed by the alert issued by speakersof control and power source module 12. In one example, status indicators72 and 74 may be lighted, e.g. LED lighted windows that indicate theoperating status of control and power source module 12 and/or implantedpump 14. For example, status indicator 72 may be illuminated to indicatethat control and power source module 12 and/or implanted pump 14 areoperating normally without error. Status indicator 74, on the otherhand, may be illuminated to indicate one or more alarm states thatindicate errors or other actionable states of control and power sourcemodule 12 and/or implanted pump 14. For example, status indicator 74 maybe illuminated to indicate the state of removable battery 24 and/or theinternal battery of control and power source module 12 as at or below athreshold charge level. In some examples, status indicator 74 may beilluminated in a variety of manners to indicate different states ofcontrol and power source module 12 and/or implanted pump 14, includingbeing illuminated in different colors to indicate alarm states ofremovable battery 24 and/or the internal battery and/or the implantbattery of different levels of severity.

Example control and power source module of FIGS. 2A-2E also includescable port 60, external power source port 62, and battery releasebuttons 64 and 66. Cable port 60 may be configured to receive cable 19via connector 26 as illustrated in FIG. 1. External power source port 62may be configured to receive one or more types of external power sourceadaptors, e.g. an AC/DC or DC/DC adaptor configured to charge removablebattery 24 and/or the internal battery of control and power sourcemodule 12.

As will be described in greater detail with reference to FIGS. 3 and 4,control and power source module 12 includes a latch configured torelease removable battery 24 from housing 22. The battery release latchof control and power source module may be, in one example, configured tobe actuated to release removable battery 24 from housing 22 by at leasttwo independent motions. In FIGS. 2A-2E, the battery release latch ofcontrol and power source module 12 includes battery release buttons 64and 66. In one example, battery release buttons 64 and 66 are biasedinto a locked position that inhibits removal of removable battery 24from housing 22 and are configured to be pushed into an unlockedposition simultaneously to release the first power source for removalfrom the housing. In the example control and power source module 12 ofFIGS. 2A-2E, battery release button 64 is arranged on right side (fromthe perspective of the views of FIGS. 2A-2E) of housing 22 and batteryrelease button 66 is arranged on opposing left side of housing 22 suchthat the two buttons are configured to be pushed in approximatelyopposite directions to one another.

FIG. 3 is an exploded view of example control and power source module 12of FIGS. 2A-2E. Example control and power source module 12 includeshousing 22, removable battery 24, internal battery 80, user interface50, cable port 60, external power source port 62, battery release latch82, circuit boards 84, 86, and 88, and speakers 90. Housing 22 includesa number of pieces, including front shield 22 a, sides and back shield22 b, top cap 22 c, main board backing 22 d, status indicator backing 22e, and status indicator bezel 22 f. As illustrated in FIG. 3, removablebattery 24 forms part of the back of control and power source module 12.Housing 22 of control and power source module 12, including one or moreof front shield 22 a, sides and back shield 22 b, top cap 22 c, mainboard backing 22 d, status indicator backing 22 e, and status indicatorbezel 22 f may be fabricated from a variety of materials, including,e.g., plastics including acrylonitrile butadiene styrene (ABS),polyvinyl siloxane (PVS), silicone, metals including stainless steel,aluminum, titanium, copper, and composites including carbon fiber,glasses, and ceramics. In some examples different portions of housing22, including front shield 22 a, sides and back shield 22 b, top cap 22c, main board backing 22 d, status indicator backing 22 e, and statusindicator bezel 22 f may be fabricated from the same materials. Inanother example, however, different portions of housing 22, includingone or more of front shield 22 a, sides and back shield 22 b, top cap 22c, main board backing 22 d, status indicator backing 22 e, and statusindicator bezel 22 f may be fabricated from different materials.

In one example, front shield 22 a of housing 22 may include a metallicbezel partially or completely surrounding display 52 of user interface50. The metallic bezel may be fabricated from a variety of thermallyconductive materials including, e.g., aluminum, copper, and alloysthereof. The metallic bezel of front shield 22 a of housing 22 may beconfigured to provide thermal conductance of heat generated by one ormore of circuit boards 84, 86, and 88, as well as internal battery 80and/or removable battery 24. In one example, a metallic bezel of frontshield 22 a is configured to sink heat generated by circuit board 86associated with user interface 50. The metallic portion of front shield22 a may be thermally coupled to circuit board 86 to increase thermalconduction between the two components, e.g., using a thermallyconductive pad, potting material, or a thermal grease interposed betweenthe shield and the circuit board. In a similar manner to front shield 22a, indicator bezel 22 f may be configured, in one example, to providethermal conductance of heat generated by circuit board 88. In such anexample, indicator bezel 22 f may be fabricated from a variety ofthermally conductive materials including, e.g., aluminum, copper, andalloys thereof and may be thermally coupled to circuit board 88 toincrease thermal conduction between the two components, e.g., using athermally conductive pad, potting material, or a thermal greaseinterposed between the shield and the circuit board.

User interface 50 of control and power source module includes display52, input buttons 54, mute button 70, and status indicators 72 and 74.Battery release latch 82 includes base 92, right and left push buttons64 and 66, respectively, and right and left back plates 94 and 96,respectively. Control and power source 12 includes a number of circuitboards, including main board 84, display board 86, and status indicatorboard 88, one or more of which may be connected to one another. In oneexample, main board 84 includes the main control electronic componentsfor control and power source module 12, including, e.g. processor(s),memory, telemetry, charging, and power management electronics. Displayboard 86 includes input buttons 54 and may include other electronicsassociated with the function of display 52. Additionally, statusindicator board 88 may include a number of electronic componentsassociated with mute button 70 and status indicators 72 and 74.

In FIG. 3, main board backing 22 d is configured to be connected tofront shield 22 a and to secure main board 84 and to help secure cableport 60 and external power source port 62, along with top cap 22 c. Mainboard 84 is interposed between top cap 22 c and main board backing 22 d.Cable port 60 and external power source port 62 are received byapertures in top cap 22 c and main board backing 22 d. Status indicatorboard backing 22 e is configured to be connected to front shield 22 aand to secure status indicator board 88 to housing 22 of control andpower source module 12. Status indicator board 88 may be connected tobacking 22 e. Each of mute button 70 and status indicators 72 and 74 arecomprised of a user interface component configured to be received bybezel 22 f and an electronic component on status indicator board 88. Inthe example of FIG. 3, mute button 70 includes a push button received inan aperture of bezel 22 f and a contact or non-contact sensor onindicator board 88. In the example of FIG. 3, status indicators 72 and74 each include a lens configured to be received in a correspondingaperture in bezel 22 f and a light emitter, e.g. an LED on statusindicator board 88. Status indicator board 88 and the push button ofmute button 72 and lenses of indicators 72 and 74 are interposed betweenmain board backing 22 e and bezel 22 f.

The sides of shield 22 b are configured to mate with and overlay thesides of front shield 22 a of housing 22 of control and power sourcemodule 12. Sides and back shield 22 b includes apertures 98 and 100.Aperture 98 is configured to receive bezel 22 f. Apertures 100 areconfigured to receive buttons 64 and 66 of battery release latch 82 andto be aligned with corresponding apertures 102 in front shield 22 a,only one of which can be seen in the view of FIG. 3. Removable battery24 is connected to housing 22 and configured to be released by batteryrelease latch 82. In particular, tabs 104 on removable battery 24 isconfigured to be received on rails 106 on the interior of front shield22 a such that the battery may slide into and out of a locked connectionwith housing 22 of control and power source module 12 via batteryrelease latch 82. Display 52, display board 86 including input buttons54, speakers 90, internal battery 80, and battery release latch 82 areconfigured to be arranged within housing 22 of control and power sourcemodule over removable battery 24. Base 92 of battery release latch 82 isconfigured to be fastened to front shield 22 a and to slidably receiveright and left push buttons 64 and 66 and back plates 94 and 96. Display52 is generally aligned with a window in front shield 22 a and inputbuttons 54 on display board 86 are generally aligned with depressions 76in the front shield of housing 22 of control and power source module 12.

In some examples, control and power source module 12 may employ avariety of waterproofing techniques and mechanisms for protectingvarious components of the device from ingress or egress of one or morematerials into or out of housing 22. In one example, removable battery24 may be electrically coupled with one or more of circuit boards 84,86, and 88 with, e.g. a multi-pin connection that employs a gasket toseal the releasable connection between battery 24 and the innercomponents of control and power source module 12 from ingress ofmaterials into housing 22. Such a gasket may be fabricated from avariety of materials, including, e.g. a compressible polymer or anelastomer, e.g. rubber. In one example, one or more parts of housing 22,e.g. one or more of front shield 22 a, sides and back shield 22 b, topcap 22 c may be hermetically sealed. For example, front shield 22 a,sides and back shield 22 b, top cap 22 c may be connected to formenclosed housing 22 by gasket(s), sonic welding or adhesives.

In one example, speakers 90 are piezoelectric speakers that areconfigured to be fastened, e.g. with an adhesive to an interior surfaceof front shield 22 a of housing 22 of control and power source module12. Piezoelectric speakers may include a piezoelectric crystal coupledto a mechanical diaphragm. Sound is produced by alternatively applyingand removing an electrical signal to the crystal, which responds byflexing and unflexing the mechanical diaphragm in proportion to thevoltage applied across the crystal's surfaces. The action of flexing andunflexing the mechanical diaphragm at relatively high frequenciesproduces vibrations in the diaphragm that emit an audible sound, e.g.sounds in a frequency range from approximately 150 Hz to approximately 4kHz.

In some examples, a portion of housing 22 may be configured to act inconjunction with speakers 90 to effectively increase the amplitude ofthe sounds emitted by the speakers. For example, the geometry of aportion of front shield 22 a of housing 22 to which speakers 90 areconnected may be shaped and sized to cause the shield to resonate inresponse to vibration of the speakers. For example, the portion of frontshield 22 a of housing 22 to which speakers 90 are connected may beshaped and sized such that the natural frequency of the combination ofhousing and speakers modulated to a target frequency within theoperational range of the speakers. Controlling speakers 90 to operate ata particular frequency may then cause the speakers and portion of frontshield 22 a to resonate, thereby effectively increasing the amplitude ofthe sounds emitted by the speakers. In one example, speakers 90 includepiezoelectric speakers that generally perform better above 1000 Hz. Assuch, the natural frequency of the combination of the portion of frontshield 22 a to which speakers 90 are attached and the speakers may bemodulated to greater than 1000 Hz.

Modulating the housing of a control and power source module toparticular resonant frequencies may be accomplished by a number ofanalytical, numerical, and experimental methods. In one example, theresonant frequency of a housing of a control and power source module maybe modulated analytically using theory for thin, elastic plates todetermine a starting point for geometry and material properties of thehousing. In another example, the resonant frequency of a housing of acontrol and power source module may be modulated numerically usingfinite element analysis (FEA) modeling to simulate the vibrationcharacteristics of different modeled geometries. Additionally, a numberof processes and techniques, such as Chladni patterns, may be employedto experimentally refine the natural frequency of the housing with thespeakers.

Although the example of FIG. 3 includes two speakers 90, other examplesmay include more or fewer speakers configured to emit audible sounds,e.g. alarms to a user of control and power source module 12. In oneexample, a control and power source module according to this disclosureincludes one speaker. In another example, a control and power sourcemodule according to this disclosure includes four speakers.

FIGS. 4A and 4B are perspective views of removable battery 24 andbattery release latch 82 of control and power source module 12.Removable battery 24 includes stops 106 configured to engage catches 108on battery release latch 82 to lock the battery in housing 22 of controland power source module 12. Battery release latch 82 includes base 92,right and left push buttons 64 and 66, respectively, right and left backplates 94 and 96, respectively, catches 108, and springs 110.

In FIGS. 4A and 4B, flanges 112 and 114 protrude from push buttons 64and 66, respectively, and are received by slots 116 and 118,respectively, in base 92. Back plates 94 and 96 are also received byslots 116 and 118 and are fastened to flanges 112 and 114 to slidablyconnect push buttons 64 and 66, respectively, to base 92 of batteryrelease latch 82. Springs 110 are interposed between a face of slots 116and 118 of base 92 and connected flanges 112 and 114 and back plates 94and 96. Springs 110 may function to bias push buttons 64 and 66 into alocked position that inhibits removal of battery 24 from housing 22 ofcontrol and power source module 12. In the example of FIGS. 4A and 4B,springs 110 are configured to bias push buttons 64 and 66 laterallyoutward, in generally opposing directions away from the outer surfacesof removable battery 24 such that catches 108 engage stops 106 onremovable battery 24 to inhibit the battery from being removed fromhousing 22 of control and power source module 12. To release battery 24from housing 22 of control and power source module 12, both of pushbuttons 64 and 66 are pushed laterally inward, in generally opposingdirections toward the interior region of removable battery 24 such thatcatches 108 move out of engagement with stops 106 on removable battery24. In one example, control and power source module 12 may be configuredwith a second mechanical latching mechanism for battery 24. For example,battery 24 may be received in housing 22 of control and power sourcemodule 12 with a friction fit such that a user must apply a thresholdforce, e.g. 1 pound force to remove the battery from the housing.

Although the example control and power source module 12 described andillustrated with reference to FIGS. 2A-4 includes battery release latch82 including push buttons 64 and 66, in another example according tothis disclosure the latch may be triggered by another mechanism thatrequires two independent motions to release a removable battery from acontrol and power source module. In one example according to thisdisclosure, a battery release latch actuated by at least two independentmotions and configured to release a removable power source from ahousing of a control and power source module may include a channel and apost biased into a locked position toward a first end of the channelthat inhibits removal of the power source from the housing. In such anexample, the post may be configured to be pushed in at least twodirections toward a second end of the channel into an unlocked positionto release the removable power source from the housing of the controland power source module. FIGS. 4C-4H illustrate a number of particularalternative latching mechanisms that may be employed in conjunction withcontrol and power source modules according to this disclosure. In eachof the examples of FIGS. 4C-4H, the control and power source moduleincludes a removable battery that may be released from and locked to ahousing by the respective example latching mechanisms. Additionally, thedirection in which the removable battery may be released from thecontrol and power source module in the illustrated examples is indicatedin each of the figures by arrow R.

FIG. 4C is a perspective view of a control and power source moduleincluding battery release latch 122. Battery release latch 122 includespaddle 122 a, two flanges 122 b (only one of which is viewable FIG. 4C),pivot 122 c and cam 122 d. In FIG. 4C, paddle 122 a and flanges 122 bare pivotably connected to the control and power source module at pivot122 c. Cam 122 d is a protrusion extending inward from paddle 122 b.Latch 122 may be actuated by rotating paddle 122 a away from the controland power source module, which causes flanges 122 b to rotate aboutpivot 122 c. Flanges 122 b turn cam 122 d, which may be received withina channel in the removable battery. Rotating cam 122 d pushes againstthe removable battery such that the battery is pushed downward and outof engagement with the control and power source module. When thebattery, or a new or replacement removable battery is reinserted intothe control and power source module of FIG. 4C a channel in the batterymay engage cam 122 d and rotating paddle 122 a, which, in turn, rotatesflanges 122 b, may cause the cam to draw the battery into the housingand lock the battery in place. In one example of latch 122, paddle 122 amay be releasably secured to the housing of the control and power sourcemodule to prevent inadvertent actuation of the latch. For example,paddle 122 a may be held to the housing by a small permanent magnet.

FIG. 4D is a perspective view of a control and power source moduleincluding battery release latch 124. Battery release latch 124 includespaddle 124 a, two flanges 124 b (only one of which is viewable FIG. 4C),pivot 124 c and post 124 d. Flanges 124 b each include two landings 122e, 122 f, which are configured to engage post when the removable batteryis released and locked into the control and power source module of FIG.4D. In FIG. 4D, paddle 124 a and flanges 124 b are pivotably connectedto the removable battery of the control and power source module at pivot124 c. Post 124 d protrudes from the housing of the control and powersource module. Latch 124 may be actuated by rotating paddle 124 a awayfrom the control and power source module, which causes flanges 124 b torotate about pivot 124 c. Flanges 124 b turn until release landing 124 fengages post 124 b. As paddle 124 a and flanges 124 c continue torotate, landing 124 f pushes against post 124 b, which causes the latchand removable battery to be released from the housing of the control andpower source module. When the battery, or a new or replacement removablebattery is reinserted into the control and power source module of FIG.4D, the battery and latch 124 may be pushed into the housing untillanding 124 f engages post 124 d, after which paddle 124 a and flanges124 b may be rotated until lock landing 124 e engages post 124 d. Aspaddle 124 a and flanges 124 c continue to rotate, landing 124 e pushesagainst post 124 b, which causes the latch and removable battery to bepulled into and locked to the housing of the control and power sourcemodule. In one example of latch 124, paddle 124 a may be releasablysecured to the housing of the control and power source module to preventinadvertent actuation of the latch. For example, paddle 124 a may beheld to the housing by a small permanent magnet.

FIG. 4E is a perspective view of a control and power source moduleincluding battery release latch 126. The control and power source moduleof FIG. 4E includes a clam shell design including two halves pivotablyconnected to one another. Battery release latch 126 includes two buttons126 a and two clips 126 b. In FIG. 4E, buttons 126 a and clips 126 b areconnected to the housing of the control and power source module. Buttons126 a are configured to cause clips 126 b to move into and out ofengagement with catches in the other half of the clam shell housing ofthe control and power source module of FIG. 4E. Latch 126 may beactuated by pushing both of buttons 126 a simultaneously to cause bothclips 126 b to move out of engagement with respective catches in theother half of the clam shell housing. In one example, the interiorsurface of the half of the housing opposite clips 126 b may includeslots that are configured to receive the clips.

FIG. 4F is a perspective view of a control and power source moduleincluding battery release latch 128. Battery release latch 128 includestwo buttons 128 a and two clips 128 b. In FIG. 4F, buttons 128 a andclips 128 b are connected to the housing of the control and power sourcemodule. Buttons 128 a are configured to cause clips 128 b to move intoand out of engagement with catches in cap 128 c of the housing of thecontrol and power source module of FIG. 4E. Latch 128 may be actuated bypushing both of buttons 128 a simultaneously to cause both clips 128 bto move out of engagement with respective catches in cap 128 c of thehousing. In one example, the interior surface of cap 128 c of thehousing may include slots that are configured to receive the clips.

FIGS. 4G and 4H are perspective views of a control and power sourcemodule including battery release latch 129. Battery release latch 129includes knob 129 a, pivot 129 b, and channel 129 c. In FIGS. 4G and 4H,knob 129 a is pivotably connected to the housing of the control andpower source module at pivot 129 b. The removable battery of the controland power source module of FIGS. 4G and 4H includes a post thatprotrudes from one end of the battery and is configured to be receivedin channel 129 c. Latch 129 may be actuated to release the battery byrotating knob 129 a about pivot 129 b. In one example, knob 129 a isrotated approximately 180 degrees about pivot 129 b. Channel 129 c isconfigured to push on the post protruding from the battery as knob 129 ais rotated such that the battery is gradually released upward away fromthe housing. After rotating knob 129 a completely, e.g. 180 degrees, thepost in the battery may be released from channel 129 c to release thebattery from the housing of the control and power source module.

FIG. 5 is a functional block diagram illustrating components of anexample of control and power source module 12, which includes removablebattery 24, internal battery 90, cable port 60 connected to cable 19 viaconnector 26, external power source port 62, speakers 90, and a varietyof electronics. The electronics of control and power source module 12include first processor 130, second processor 132, memory 134, firsttelemetry module 136, second telemetry module 138, power managementmodule 140, charger 142 and charger switch 144, power junction 146, andpower transfer inverter or power bridge 148. Control and power sourcemodule 12 includes speakers 90 driven by driver 150 for emitting audiblesounds, such as alarms to patient 20 or a caregiver, such as aclinician. As illustrated in the example of FIG. 5, control and powersource module 12 may also include one or more sensors 152, including,e.g. motion or light sensors. In one example, sensors 152 includes anambient light sensor that is configured to automatically adjust thecontrast and/or brightness of display 52 of user interface 50 based oncurrent ambient light conditions.

Control and power source module 12 is configured to provideuninterrupted power to components of a VAD, e.g. implanted pump 14, byemploying one removable battery 24 as a primary power source andinternal battery 80 as a back-up to bridge operation of the control andpower source module components during recharge of removable battery 24.Internal battery 80 may be non-removably connected to control and powersource module 12 in the sense that it is not configured to be removedand replaced by users during normal operation of the device. In someexamples, internal battery 80 may, of course, be removed from controland power source module 12, e.g. by disassembling the device anddisconnecting the internal battery from the internal circuitry of thedevice. In one example, one or both of removable battery 24 and internalbattery 80 of control and power source module 12 may include, e.g.,rechargeable lithium-ion (Li-ion), lithium polymer (Lipoly),nickel-metal hydride (NiMH), or nickel-cadmium (NiCd) battery cells. Inone example, removable battery 24 includes rechargeable lithium-ion(Li-ion), nickel-metal hydride (NiMH), or nickel-cadmium (NiCd) batterycells, while internal battery 80 includes lithium polymer (Lipoly)battery cells.

Control and power source module 12 employs two power sources forredundancy and continuous operation. The primary power source isremovable battery 24, which may be removed to recharge the battery, e.g.using a separate charging station. Internal battery 80 is generallynon-removable and, in some examples, may be charged by either removablebattery 24 or an external power source. Although control and powersource module 12 is described as including removable battery 24 as theprimary power source, the module also includes an adapter, externalpower source port 62 for a DC or AC source. An external power sourceconnected to control and power source module 12 via port 62 may functionnot only to charge removable battery 24 and internal battery 80, butalso as a third source of power for the device. In one example, such anexternal power source may be employed by control and power source module12 over both removable battery 24 and internal battery 80 to powercomponents of the device, as well as, e.g., implanted pump 14.

Control and power source module 12 may contain only the primary powersource, removable battery 24, which may be removed to recharge thebattery, e.g. using a separate charging station. An implant battery inimplant controller 21 may be employed for redundancy and continuousoperation. In some examples, the implant battery, may be charged byeither removable battery 24 or an external power source through thepower transfer to the battery charger in the implantable controller.Although control and power source module 12 is described as includingremovable battery 24 as the primary power source, the module alsoincludes an adapter, external power source port 62 for a DC or ACsource. An external power source connected to control and power sourcemodule 12 via port 62 may function not only to charge removable battery24 and the implant battery, but also as a third source of power for thedevice. In one example, such an external power source may be employed bycontrol and power source module 12 over both removable battery 24 andthe implant battery to power components of the device, the implantcontroller 21, as well as, e.g., implanted pump 14.

In examples according to this disclosure, in addition to connecting anexternal power source to control and power source module 12 as a thirdpower source, removable battery 24 may be replaced by an external powersource, including, e.g., an alternating or direct current (AC or DCrespectively) power supply. In one such example, removable battery 24may include an adapter to which the external power source may connect.As another alternative to the configuration illustrated in the exampleof FIG. 5, in the event that patient 20 desires a longer runtime betweencharges than removable battery 24 provides, control and power source 12may be configured to have an enlarged removable battery connected to thedevice. In one example the enlarged removable battery may include twicethe capacity of removable battery 24, but may also be significantlylarger than battery 24. In any event, such an enlarged removable batterymay be connected to control and power source module 12, e.g., via port62 or through a port on removable battery 24.

Referring again to the example of FIG. 5, removable battery 24 andback-up internal battery 80 may be configured to have the same ordifferent operational life times between successive charges.Additionally, removable battery 24 and back-up internal battery 80 maybe rated for the same or different number of charge cycles beforerequiring replacement. In one example, removable battery 24 isconfigured to operate without recharge for a period of time in a rangefrom approximately 4 hours to approximately 8 hours. In another example,removable battery 24 is configured to operate without recharge for aperiod of time approximately equal to 6 hours. In one example, internalbattery 80 is configured to operate without recharge for a period oftime in a range from approximately 30 minutes to approximately 2 hours.In one example, internal battery 80 is configured to operate withoutrecharge for a period of time approximately equal to 1 hour. Employing asmaller internal battery 80 in control and power source module 12 mayact to reduce the size, complexity, and cost of the device by removingthe necessity for two full-size external batteries and a mechanicalbattery locking mechanism.

In one example, removable battery 24 is a 4S2P battery with four batterycells in series and two in parallel. Removable battery 24 may include a3 amp-hour (Ah), 14.4 volt battery that is configured to operate in arange from approximately 500 to approximately 1000 recharging cyclesbefore necessitating replacement. The operating lifetime of removablebattery 24 over the approximately 500 to approximately 1000 rechargingcycles may, in one example, equate to approximately one year. In oneexample, internal battery 80 is a 4S1P battery with four battery cellsin series and one in parallel. Internal battery 80 may include a 100milliamp-hour (mAh), 14.4 volt battery that is configured to operate forapproximately 500 recharge cycles before necessitating replacement. Asnoted above, in examples according to this disclosure, internal battery80 may be non-removably connected to control and power source module 12in the sense that it is not configured to be removed and replaced byusers during normal operation of the device. However, internal battery80 may be removed from control and power source module 12, e.g. bydisassembling the device and disconnecting the internal battery from theinternal circuitry of the device in order to, e.g. replace the batteryafter it is no longer capable of holding a charge.

Control and power source module 12 includes power management module 140,which may be embodied as a variety of hardware and/or softwarecomponents. In one example, power management module 140 may be one ormore algorithms stored on memory 134 and executed by one or both offirst processor 130 and second processor 132 of control and power sourcemodule 12. In any event, power management module 140 may be configuredto manage the charging of the power sources of control and power sourcemodule 12, which of the power sources delivers powers to whichcomponents under different operational modes of the device, andcommunicate the status of the power sources to users, e.g. via one ormore elements of user interface 50.

In one example of control and power source module 12 of FIG. 5, powermanagement module 140 manages the charging of removable battery 24 andinternal battery 80. For example, power management module 140 maycontrol the operation of charger 142 and charger switch 144 toselectively charge one or both of removable battery 24 and internalbattery 80. As noted above, control and power source module 12 includesexternal power source port 62 for connecting a third external powersource to the device. In examples in which a third source is employed topower some or all of the components of control and power source module12, the device may also employ flexible on-board charging techniques toprovide users the ability to charge removable battery 24 and/or internalbattery 80 while connected to the device. The third power source may beeither an additional external battery or another external power source,e.g. a DC or AC external power source.

In one example, charger switch 144 may include a series of field-effecttransistors (FETs) or other switches may allow one or more algorithms,e.g. stored on memory 134 and executed by power management module 140 ofcontrol and power source module 12 to control which of removable battery24 or internal battery 80 is being charged at a given time andoperational state of module 12. Additionally, in one example, powermanagement module 140 may control charger 142 and/or charger switch 144of control and power source module 12 to select either removable battery24 or preferably the third external power source connected via port 62to be employed for charging the other power sources of the device. Thecomponents associated with charger 142 and charger switch 144 of controland power source management module 12 are described in detail below withreference to the example circuits of FIG. 12. In one example, the sameor different algorithms executed by power management module 140 tocontrol which power source of control and power source module 12 ischarged may also control the battery charge profile based on the stateof removable battery 24 and internal battery 80 and, if connected viaport 62, the third external power source.

When employed for use with a VAD or other MCS, power will be deliveredby control and power source module 12 to implanted pump controller 21primarily from removable battery 24. If battery 24 becomes depleted andrequires removal and recharging, or, if the removable battery fails,power management module 140 of control and power source module 12 mayautomatically toggle to internal battery 80 or to an external powersource connected to the device via port 62. Power management module 140accomplishes this multiplexing of power sources associated with controland power source module 12 via power junction 146 in the example of FIG.5.

In one example, power junction 146 may include a number of ideal diodesconnected to removable battery 24, internal battery 80, and, ifconnected to control and power source module 12 via port 62, a thirdexternal power source. The ideal diodes of such an example of powerjunction 146 may be configured to automatically select the power sourceconnected to control and power source module 12 with the highestvoltage. In some examples of control and power source module 12,however, removable battery 24 and internal battery 80 may be configuredto operate at approximately the same voltage. In such an example, asmall amount of discharge of removable battery 24 may cause theoperating voltage of the removable battery to fall below internalbattery 80, which, without intervention would cause the ideal diodes ofpower junction 146 to select the internal battery after only a smallamount of use of the removable battery. As such, in one example, inaddition to the ideal diodes, power junction 146 may include a switchcontrolled by power management module 140 that may function to overridethe diodes, under some conditions, to select removable battery 24 topower components of control and power source module 12 and implantedpump 14 over internal battery 80.

Power management module 140 may control the switch of power junction 146to select removable battery 24 to deliver power until the removablebattery has been deleted to a threshold charge level, at which point,the power management module 140 may, e.g., deactivate the switch toallow the ideal diodes of power junction 146 to select internal battery80. In one example, power management module 140 in conjunction withpower junction 146 may be configured to select an external power sourceto power components of control and power source module 12 and implantedpump 14 over removable battery 24 and internal battery 80 whenever sucha source is connected the device via port 62. In one example, powermanagement module 140 in conjunction with power junction 146 may beconfigured to select the external power source regardless of the levelof charge on removable battery 24 of internal battery 80. Additionaldetails of power junction 146 is described in detail below withreference to the example circuits of FIG. 11.

Regardless of the particular configuration of power junction 146, powermanagement module 140 may monitor the power sources connected to controland power source module 12 and selectively activate one of the powersources depending on the operating conditions of the device. Forexample, power management module 140 may monitor which of removablebattery 24, internal battery 80, and an external power source areconnected to control and power source module 12 to determine which ofthe connected sources should be used to power components of module 12,as well as implanted pump 14. Additionally, power management module 140may monitor removable battery 24 and internal battery 80 to selectivelyactivate one of the batteries based on the level of charge remaining onthe batteries. For example, while removable battery 24 is being used,back-up internal battery 80 may be periodically tested by powermanagement module 140 to determine a level of charge left in theinternal battery. In the event removable battery 24 drops below athreshold charge level, power management module 140 may activateinternal battery 80, provided, in some examples, the internal batteryhas at least a threshold amount of charge left.

Power management module 140, alone or in conjunction with power junction146 may be configured to selectively activate one of the power sourcesof module 12 based on reasons other than the voltage delivered by thepower source and the charge level remaining on the power source. Forexample, power management module 140 may be configured to selectivelyactivate one of removable battery 24 or internal battery 80 based on thesource and amplitude of a particular power requirement. As noted above,removable battery 24 and internal battery 80 may include rechargeablebatteries with a variety of chemistries, including, e.g., lithium-ion(Li-ion), lithium polymer (Lipoly), nickel-metal hydride (NiMH), ornickel-cadmium (NiCd). In addition to removable battery 24 and internalbattery 80 including particular chemistries, each of the batteries ofcontrol and power source module 12 may be configured with particularperformance characteristics, based upon which, in some examples, powermanagement module 140 may selectively activate one of the batteries.

In one example according to this disclosure, control and power sourcemodule 12, or another such device according to this disclosure, includesone energy dense power source and one power dense power source. Forexample, removable battery 24 of control and power source module 12 maybe an energy dense power source and internal battery 80 may be a powerdense power source. In another example, removable battery 24 of controland power source module 12 may be a power dense power source andinternal battery 80 may be an energy dense power source. An energy densepower source may be a power source that is designed to maximize thetotal amount of energy per unit volume that the source can deliver. Inthe case of a rechargeable battery, an energy dense power source may bea battery that is designed to maximize the total amount of energy perunit volume that the source can deliver between successive charges. Apower dense power source, on the other hand, may be a power source thatis designed to maximize the power per unit volume that the source candeliver at any given time, e.g. to accommodate large power loads.

In one example, removable battery 24 of control and power source module12 may be an energy dense power source including an energy density in arange from approximately 455 to approximately 600 watt-hours per liter(W-hr/L). In one example, internal battery 80 may be a power dense powersource including a power density in a range from approximately 700 wattsper liter (W/L) to approximately 6 kilowatts per liter (kW/L). In oneexample in which removable battery 24 of control and power source module12 is an energy dense power source and internal battery 80 is a powerdense power source, power management module 140 may be configured toselectively activate one of removable battery 24 or internal battery 80based on the amplitude of a particular power requirement. For example,implanted pump 14 may have transient operating conditions whichtemporarily cause large spikes in the power drawn by the pump. In oneexample, starting implanted pump 14 may draw a significantly largeramount of power than running the pump at steady state, e.g. start-up maydraw approximately 50 watts while steady state draws approximately 5watts. In another example, transient physiological conditions of patient20 may cause large power draws from pump 14. In examples including largepower spikes in the power requirements of, e.g. implanted pump 14, powermanagement module 140 may selectively activate internal battery 80, e.g.by controlling power junction 146, regardless of the charge level ofremovable batter 24, because the power dense internal battery may bebetter adapted for handling the power spike than the energy denseremovable battery.

In addition to managing power source charging and selectively activatingpower sources for power delivery, as described in the foregoingexamples, power management module 140 may also be configured to managecommunicating the status of the power sources to users, e.g. via one ormore elements of user interface 50. An example process by which powermanagement module 140 of control and power source 12 may managecommunicating the status of the power sources of the device to users isillustrated in the state diagram of FIG. 6. Functions and appearances ofan example configuration of the elements of user interface 50 of controland power source module 12 are illustrated in FIGS. 7A-9C, some of whichare described with reference to the state diagram of FIG. 6 by whichpower management module 140 of control and power source 12 managescommunicating the status of the power sources of the device to users inone example according to this disclosure.

FIG. 6 illustrates states 170-194 of the power sources connected tocontrol and power source module 12, e.g. removable battery 24, internalbattery 80, and, in some examples, an external power source connectedvia port 62. The state diagram of FIG. 6 is organized such that movementbetween states from the left side to the right of the diagram indicatesstates in which removable battery 24 is disconnected from andreconnected to control and power source module 12. Additionally, thestate diagram of FIG. 6 is organized such that movement between statesfrom the top to the bottom of the diagram indicates states in which oneor both of one or both of removable battery 24 and internal battery 80are progressively depleted to different threshold charge levels.

The state diagram of FIG. 6 uses a number of abbreviations. In FIG. 6,“batt” generally refers to battery. Each of states 170-194 include astate description, e.g. “Normal” for state 170, status and userinterface indications related to each of removable battery 24 andinternal battery 80, e.g. “E: OK, GRN, BLK” for removable battery 24 and“I: OK, GRN, BLK” for internal battery 80, and alarms communicated tousers via user interface 50. With reference to the status and userinterface indications related to each of removable battery 24 andinternal battery 80, the abbreviations used in FIG. 6 have the followingmeanings The first letter, e.g. E or I, refers to which of removablebattery 24 or internal battery 80, respectively, the status and userinterface indications relates. The first letter E, as well as theabbreviation Ext in the state description refers to an external battery,which in the example of FIG. 6 is equivalent to a removable battery,such as removable battery 24 of control and power source module 12. Forboth the removable battery 24 and internal battery 80, the status anduser interface indications are the charge and operational state of thebattery, the color of the alarm indication on user interface 50, and thecolor of the graphical representation of the battery on user interface50. For example, in state 170, “E: OK, GRN, BLK” means that removablebattery 24 is above a low charge level threshold and is operatingproperly (OK), the color of the alarm indication on user interface 50 isgreen (GRN), and the color of the graphical representation of thebattery on user interface 50 is black (BLK).

In the state diagram of FIG. 6, alarm and battery representation color“YLW” stands for yellow and “RED” indicates the color red. In the eventremovable battery 24 is disconnected from control and power sourcemodule 12, the state of the battery is indicated in FIG. 6 as “DC,”which stands for disconnected. Additionally, both removable battery 24and internal battery 80 include three threshold charge levels, indicatedby “OK, LOW, and EMPTY.” The battery condition OK, as far as chargelevel is concerned, indicates that the battery to which the conditionrefers is above a threshold low charge level, while LOW indicates thebattery is at a threshold low charge level, which may be a range ofcharge levels, and EMPTY indicates the battery is at a threshold emptycharge level, which may also be a range of charge levels and which maybe greater than zero charge. The threshold charge levels for removablebattery 24 and internal battery 80 employed in examples according tothis disclosure may be the same or different, in number as well asmagnitude.

Starting in the upper right hand corner of the state diagram of FIG. 6,state 170 indicates a normal operational state for control and powersource module 12. In state 170, removable battery 24 and internalbattery 80 are both above a threshold low charge level, and there stateis thus indicated in state 170 as OK. The indication in state 170 thatremovable battery 24 and internal battery 80 are both OK because thebatteries are above a threshold low charge level does not necessarilymean that the batteries are fully charged and may occur regardless ofwhether control and power source module 12 is connected to an externalpower source to charge one or both of the batteries. For example, state170 may occur when removable battery 24 is partially discharged, but thecharge level of the battery is still above a low threshold level thatmay necessitate alerting the user and recharging. Similarly, state 170may occur when internal battery 80 is partially discharged, but thecharge level of the battery is still above a low threshold level thatmay necessitate alerting the user and recharging. State 170 may alsooccur when both removable battery 24 and internal battery 80 arepartially discharged, but the charge levels of both the batteries arestill above a low threshold level that may necessitate alerting the userand recharging. In another example, state 170 may occur when bothremovable battery 24 and internal battery 80 are fully charged and whenan external power source is connected to control and power source module12, as long as both batteries are also above a threshold low chargelevel.

FIGS. 7A and 7B illustrate examples of the manner in which powermanagement module 140 may control user interface 50 when control andpower source module 12 is in the normal operational state indicated bystate 170 in FIG. 6. As described above, user interface 50 of controland power source module 12 includes display 52, input buttons 54, aswell as mute button 70 and status indicators 72 and 74. In the examplesof FIGS. 7A and 7B, display 52 includes removable battery icon 200,internal battery icon 202, and status indicator 204. Also in theexamples of FIGS. 7A and 7B, as well as FIGS. 8-10B, input buttons 54are encoded with two different icons, one a rectangular icon and theother a triangular icon. In these examples of user interface 50, inputbuttons 54 correspond to two main functions for interacting with controland power source module 12. Input button 54 encoded with the rectangularicon may function as a “home” button that, when activated by a user,navigates to a default screen presented on display 52 of user interface50. Input button 54 encoded with the triangular icon may function as a“next” button that, when activated by a user, toggles to the next screenin a series of possible screens that may be presented on display 52 ofuser interface 50.

FIG. 7A illustrates an example in which removable battery 24 andinternal battery 80 of control and power source module 12 are fullycharged, as indicated by the amount of fill in removable battery icon200 and internal battery icon 202 associated with removable and internalbatteries 24 and 80, respectively. In FIG. 7A, neither removable battery24 or internal battery 80 are currently being charged, e.g. either by anexternal power source connected to control and power source module 12via port 62 or, in the case of internal battery 80 by removable battery24.

As the conditions of removable battery 24 and internal battery 80, aswell as various other components of control and power source module 12,in FIG. 7A indicate a normal operating state corresponding to state 170from FIG. 6, status indicator 204 on display 52 presents a heart icon.Additionally, status indicator 72 is activated by control and powersource module 12 to illuminate the heart shaped indicator. Finally,because the conditions of removable battery 24 and internal battery 80,as well as various other components of control and power source module12, indicate a normal operating state that does not necessitate anyalarms, display 52 does not present any alarm icons and status indicator74 associated with alarm conditions is not illuminated.

FIG. 7B illustrates an example in which removable battery 24 andinternal battery 80 of control and power source module 12 are less thanfully charged, but are above a threshold low charge level, as indicatedby the amount of fill in graphics 200 and 202 associated with removableand internal batteries, respectively. Additionally, in FIG. 7B, bothremovable battery 24 and internal battery 80 are currently beingcharged, as indicated by charging icon 206 overlaid on removable batteryicon 200 and internal battery icon 202. As described above, removablebattery 24 may be charged while connected to control and power sourcemodule 12 by an external power source connected to module 12 via port62. Additionally, internal battery 80 may be charged by the externalpower source or removable battery 24. As the conditions of removablebattery 24 and internal battery 80, as well as various other componentsof control and power source module 12, in FIG. 7B indicate a normaloperating state corresponding to state 170 from FIG. 6, as with thestate of the device illustrated in FIG. 7A, status indicator 204 ondisplay 52 presents a heart icon, status indicator 72 is illuminated,and status indicator 74 associated is not illuminated.

In both FIGS. 7A and 7B, power management module 140 may present controlbattery icon 200 and internal battery icon 202 in black, while thecharge level of removable battery 24 and internal battery 80 indicatedby the fill in battery icon 200 and internal battery icon 202, as wellas status indicator 204 on display 52 and status indicator 72 may bepresented in green, as indicated by state 170 in FIG. 6.

Referring again to FIG. 6, moving from state 170 to the right, state 172indicates that removable battery 24 is disconnected from control andpower source module 12, while internal battery 80 is above a thresholdlow charge level. State 172 indicates the disconnection of removablebattery 24 as DC. In the example state diagram of FIG. 6, wheneverremovable battery 24 is disconnected from control and power sourcemodule 12, the alarm color is indicated not by a color but by a symbol,which is abbreviated in the states of FIG. 6 as “SYM.” An example ofthis disconnection symbol is illustrated in the example of userinterface 50 in FIG. 8. Removable battery 24 may disconnect from controland power source module 12 for a variety of reasons. In one example, auser, e.g. patient 20 may have more than one removable battery that maybe connected to control and power source module 12 such that it ispossible to always or nearly always have a fully charged removablebattery that can be swapped for a discharged battery. In anotherexample, removable battery 24 may malfunction and necessitate completereplacement. In another example, removable battery 24 may reach itsmaximum number of charge cycles such that it is no longer able to hold acharge and thus necessitates complete replacement.

FIG. 8 illustrates an example of the manner in which power managementmodule 140 may control user interface 50 when control and power sourcemodule 12 is in the disconnected removable battery state indicated bystate 172 in FIG. 6. In the example of FIG. 8, display 52 includesremovable battery icon 200, internal battery icon 202, status indicator204, and disconnect symbol 206. FIG. 8 illustrates an example in whichremovable battery 24 is disconnected from control and power sourcemodule, as indicated by disconnect symbol 206 overlaid on removablebattery icon 200. Internal battery 80 of control and power source module12, as indicated in state 172 in FIG. 6, is above a threshold low chargelevel, and, in particular in FIG. 8 is fully charged, as indicated bythe amount of fill in internal battery icon 202. In FIG. 8, neitherremovable battery 24 or internal battery 80 are currently being charged,e.g. either by an external power source connected to control and powersource module 12 via port 62 or, in the case of internal battery 80 byremovable battery 24.

As the conditions of internal battery 80, as well as various othercomponents of control and power source module 12, in FIG. 8 do notindicate any alarm conditions, power management module 140 may presentstatus indicator 204 on display 52 as a heart icon. Additionally, statusindicator 72 is activated by power management module 140 to illuminatethe heart shaped indicator. Finally, because the condition of controland power source module 12 does not the necessity for any alarms,display 52 does not present any alarm icons and status indicator 74associated with alarm conditions is not illuminated.

In FIG. 8, power management module 140 may present battery icon 200,internal battery icon 202, and disconnect symbol 206 in black, while thecharge level of internal battery 80 indicated by the fill in internalbattery icon 202, as well as status indicator 204 on display 52 andstatus indicator 72 may be presented in green, as indicated by state 172in FIG. 6.

Referring again to FIG. 6, moving from state 172 to the right, state 174indicates that disconnection timeout has been reached, which causespower control module 140 to trigger an alarm instructing a user ofcontrol and power source module 12 to reconnect removable battery 24 oranother such power source to the device. The disconnection timeout inthe example of FIG. 6 is indicated as five minutes such that leavingremovable battery 24 disconnected from control and power source module12 for more than five minutes will trigger a battery reconnection alarm.However, in other examples according to this disclosure, thedisconnection timeout may be more or less time than in the example ofFIG. 6. For example, the disconnection timeout may be equal to tenminutes such that power management module 140 will trigger a batteryreconnection alarm after leaving removable battery 24 disconnected fromcontrol and power source module 12 for more than ten minutes. In oneexample of state 174, power management module 140 may control userinterface 50 to present instructions to a user of control and powersource module 12 on display 52 to insert a new or recharged removablebattery after the disconnection timeout has been reached. In anotherexample, power management module 140 may also control speaker driver 150and speakers 90 to cause the speakers to issue and audible sound.

In the example of FIG. 6, moving down from normal state 170 to state 188the charge levels of removable battery 24 and internal battery 80 getprogressively lower. Additionally, moving down from normal state 170 tostate 188 the alarms issued by power management module 140 and theinstructions associated with such alarms increase in severity, e.g. bychanging graphical symbols, color, and/or the amplitude of audiblesounds issued by speakers 90 of control and power source module 12. Instate 176, removable battery 24 has reached a threshold low chargelevel, while internal battery 80 remains above a threshold low chargelevel. In state 178, removable battery 24 has reached a threshold emptycharge level, while internal battery 80 remains above a threshold lowcharge level. In state 178, because removable battery 24 has reached athreshold empty charge level, power management module 140 of control andpower source module 12 triggers a low battery alarm. In one example ofstate 18, user interface 50 may illuminate status indicator 74 andpresent status indicator 204 on display 52 as an alarm icon.Additionally, user interface 50 may present a user of control and powersource module 12 an indication on display 52 of the low battery chargelevel, e.g. by coloring part or all of a removable battery icon ondisplay 52 yellow. In state 180, removable battery 24 has reached athreshold empty charge level and internal battery 80 has reached athreshold low charge level. Finally, in state 188, removable battery 24and internal battery 80 have both reached a threshold empty chargelevel.

In addition to the charge levels of removable battery 24 and internalbattery 80 progressively lowering moving down from state 170 to state188 in the example of FIG. 6, the alarms issued by power managementmodule 140 and the instructions associated with such alarms increase inseverity, e.g. by changing graphical symbols and colors associated withelements of user interface 50 and/or changing the amplitude of audiblesounds issued by speakers 90 of control and power source module 12. Forexample, while the alarm associated with the empty removable battery andok internal battery state 178 may include user interface 50 presenting auser of control and power source module 12 an indication on display 52of the low battery charge level, e.g. by coloring part or all of aremovable battery icon on display 52 yellow, the alarm associated withthe empty removable battery and low internal battery state 180 mayinclude presenting the user instructions on display 52 to insert a newbattery. In one such example, the priority of the alarm instructing theuser to insert a new battery, as indicated, e.g., by the amplitude of asound issued by speakers 90, may be medium.

In the empty removable battery and empty internal battery state 188, incontrast to both states 178 and 180, power management module 140 mayfurther increase the severity of the alarms presented to the user ofcontrol and power source module. As indicated in FIG. 6, for example,power management module 140 may color alarms and battery icons presentedby user interface 50 on display 52 red and may also issue instructionsto the user to insert a new battery and/or connect control and powersource module 12 to an external power source, e.g. via port 62. In onesuch example, the priority of the alarm instructing the user to insert anew battery and/or connect control and power source module 12 to anexternal power source, as indicated, e.g., by the amplitude of a soundissued by speakers 90, may be high.

Referring again to state 180 in the example of FIG. 6, moving to theright from state 180 indicates situations in which internal battery 80maintains a charge at a threshold low charge level, but the state ofremovable battery 24 changes, including disconnecting and reconnectingor replacing the removable battery. In state 182, removable battery 24is disconnected from control and power source module 12 and internalbattery 80 is at a threshold low charge level. In state 182, powermanagement module 140 may issue an alarm to a user of control and powersource module 12, including, e.g., controlling user interface 50 topresent a symbol associated with a removable battery icon indicatingthat battery 24 has been disconnected and to color part or all of aninternal battery icon on display 52 yellow. Power management module 140may also present instructions on display 52 to insert a new battery, aswell as indicating the priority of the alarm instructing the user toinsert a new battery as medium by, e.g., controlling speakers 90 toissue an audible sound at a particular amplitude.

In state 184, a removable battery at a threshold low charge level isconnected to control and power source module 12 and internal battery 80is at a threshold low charge level. In one example of state 184,removable battery 24 has been recharged to the threshold low chargelevel and reconnected to control and power source module 12. In anotherexample, however, removable battery 24 has been replaced by anotherremovable battery, which is at the threshold low charge level and whichis connected to control and power source module 12. In state 184, powermanagement module 140 may issue an alarm to a user of control and powersource module 12, including, e.g., controlling user interface 50 tocolor part or all of a removable battery icon and an internal batteryicon on display 52 yellow, present instructions on display 52 to inserta new battery, as well as indicating the priority of the alarminstructing the user to insert a new battery as medium by, e.g.,controlling speakers 90 to issue an audible sound at a particularamplitude.

In state 186, a removable battery above a threshold low charge level isconnected to control and power source module 12 and internal battery 80is at a threshold low charge level. In one example of state 186,removable battery 24 has been recharged to above the threshold lowcharge level and reconnected to control and power source module 12. Inanother example, however, removable battery 24 has been replaced byanother removable battery, which is charged above the threshold lowcharge level and which is connected to control and power source module12. In state 186, power management module 140 may issue an alarm to auser of control and power source module 12, including, e.g., controllinguser interface 50 to color part or all of a removable battery icon greento indicate that the removable battery is above the threshold low chargelevel and controlling user interface 50 to color part or all of aninternal battery icon on display 52 yellow to indicate that internalbattery 80 is still at the threshold low charge level.

Referring again to state 188 in the example of FIG. 6, moving to theright from state 188 indicates situations in which internal battery 80maintains a charge at a threshold empty charge level, but the state ofremovable battery 24 changes, including disconnecting and reconnectingor replacing the removable battery. In state 190, removable battery 24is disconnected from control and power source module 12 and internalbattery 80 is at a threshold empty charge level. In state 190, powermanagement module 140 may issue an alarm to a user of control and powersource module 12, including, e.g., controlling user interface 50 topresent a symbol associated with a removable battery icon indicatingthat battery 24 has been disconnected and to color part or all of aninternal battery icon on display 52 red. Power management module 140 mayalso present instructions on display 52 to insert a new battery and/orconnect control and power source module 12 to an external power source,as well as indicating the priority of the alarm instructing the user toinsert a new battery as high by, e.g., controlling speakers 90 to issuean audible sound at a particular amplitude, e.g. a higher amplitude thana sound issued for a medium priority alarm.

In state 192, a removable battery at a threshold low charge level isconnected to control and power source module 12 and internal battery 80is at a threshold empty charge level. In one example of state 192,removable battery 24 has been recharged to the threshold low chargelevel and reconnected to control and power source module 12. In anotherexample, however, removable battery 24 has been replaced by anotherremovable battery, which is at the threshold low charge level and whichis connected to control and power source module 12. In state 192, powermanagement module 140 may issue an alarm to a user of control and powersource module 12, including, e.g., controlling user interface 50 tocolor part or all of a removable battery icon yellow and an internalbattery icon on display 52 red, as well as present instructions ondisplay 52 to connect control and power source module 12 to an externalpower source.

In state 194, a removable battery above a threshold low charge level isconnected to control and power source module 12 and internal battery 80is at a threshold empty charge level. In one example of state 194,removable battery 24 has been recharged to above the threshold lowcharge level and reconnected to control and power source module 12. Inanother example, however, removable battery 24 has been replaced byanother removable battery, which is charged above the threshold lowcharge level and which is connected to control and power source module12. In state 194, power management module 140 may issue an alarm to auser of control and power source module 12, including, e.g., controllinguser interface 50 to color part or all of an internal battery icon ondisplay 52 red to indicate that internal battery 80 is still at thethreshold empty charge level. As internal battery 80 is still at thethreshold empty charge level, power management module 140 may alsopresent instructions on display 52 to connect control and power sourcemodule 12 to an external power source to charge the internal batteryabove the empty threshold without depleting the removable battery.

The foregoing example of the state diagram of FIG. 6 is described bybeginning with state 170 in the upper right hand corner of the diagramand moving in a number of directions from that state. However, theselection of state 170 as a starting point as well as the movements fromthere to other states described below is arbitrary and does not indicateany required order for the states of control and power source module 12.The arrows in the state diagram of FIG. 6 illustrate that movementbetween the various states of control and power source module 12 mayoccur as a result of a number of different factors, including, e.g.removing or inserting a removable battery, depleting or increasing thecharge level of one or both of removable battery 24 and internal battery80 to a number of different thresholds, and charging one or both ofremovable battery 24 and internal battery 80.

FIGS. 9A-10B illustrate a number of additional example functions andappearances of an example configuration of the elements of userinterface 50 of control and power source module 12. FIGS. 9A-Cillustrate a number of examples of user interface 50 by which powermanagement module 140 indicates three states of control and power sourcemodule 12 with removable battery 24 and internal battery 80 at varyingcharge levels. In the examples of FIGS. 9A-C, neither removable battery24 or internal battery 80 are currently being charged, e.g. either by anexternal power source connected to control and power source module 12via port 62 or, in the case of internal battery 80 by removable battery24.

FIG. 9A illustrates examples of the manner in which power managementmodule 140 may control user interface 50 when removable battery 24 is ata threshold low charge level and internal battery 80 is above athreshold charge level. In one example of the state represented by userinterface 50 in FIG. 9A, power management module 140 may present statusindicator 204 on display 52 as an alarm icon. In the example of FIG. 9A,status indicator 204 indicates the lowest level alarm condition byoutlining the alarm icon and presenting no emphasis symbols. Statusindicator 72 is also deactivated by power management module 140 suchthat the heart shaped indicator is not illuminated and status indicator74 is illuminated to indicate the alarm condition. In the example ofFIG. 9A, status indicator 204 indicates the lowest level alarm conditionby illuminating the triangle portion of the indicator withoutilluminating the emphasis symbols indicated as two curved lines in FIG.9A. In one example, power management module 140 may present removablebattery icon 200 and internal battery icon 202 in black, while thecharge level of removable battery 24 indicated by the fill in batteryicon 200, as well as status indicator 204 on display 52 and statusindicator 74 may be presented in yellow. Power management module maypresent the charge level of internal battery 80 indicated by the fill inbattery icon 202 as green to indicate, in contrast to removable battery24, the internal battery is above a threshold low charge level.

FIG. 9B illustrates examples of the manner in which power managementmodule 140 may control user interface 50 when both removable battery 24and internal battery 80 are at a threshold low charge level. In oneexample of the state represented by user interface 50 in FIG. 9B, powermanagement module 140 may present status indicator 204 on display 52 asan alarm icon. In the example of FIG. 9B, status indicator 204 indicatesa medium level alarm condition by filling the alarm icon and presentingone emphasis symbol represented by a thickened curved line. Statusindicator 72 is also deactivated by power management module 140 suchthat the heart shaped indicator is not illuminated and status indicator74 is illuminated to indicate the alarm condition. In the example ofFIG. 9B, status indicator 204 indicates the medium level alarm conditionby illuminating the triangle portion of the indicator and illuminatingone of the two emphasis symbols indicated as two curved lines in FIG.9B. In one example, power management module 140 may present removablebattery icon 200 and internal battery icon 202 in black, while thecharge level of removable battery 24 and internal battery 80 indicatedby the fill in battery icons 200 and 202, as well as status indicator204 on display 52 and status indicator 74 may be presented in yellow.

FIG. 9C illustrates examples of the manner in which power managementmodule 140 may control user interface 50 when both removable battery 24and internal battery 80 are at a threshold empty charge level. In oneexample of the state represented by user interface 50 in FIG. 9C, powermanagement module 140 may present status indicator 204 on display 52 asan alarm icon. In the example of FIG. 9C, status indicator 204 indicatesa high level alarm condition by filling the alarm icon and presentingtwo emphasis symbols represented by two thickened curved lines. Statusindicator 72 is also deactivated by power management module 140 suchthat the heart shaped indicator is not illuminated and status indicator74 is illuminated to indicate the alarm condition. In the example ofFIG. 9C, status indicator 204 indicates the high level alarm conditionby illuminating the triangle portion of the indicator and illuminatingboth emphasis symbols indicated as two curved lines in FIG. 9C. In oneexample, power management module 140 may present removable battery icon200 and internal battery icon 202 in black, while the charge level ofremovable battery 24 and internal battery 80 indicated by the fill inbattery icons 200 and 202, as well as status indicator 204 on display 52and status indicator 74 may be presented in red.

FIGS. 10A and 10B illustrate screens that may be presented by display 52of user interface 50 in addition to the screens indicating batterycharge state and alarm conditions. FIG. 10A illustrates an example inwhich power management module 140 presents various parameters related tothe implanted pump 14. As described below, power management module 140,in conjunction with power bridge 148 illustrated in FIG. 5, may beconfigured to detect the operational parameters of the motor drivingimplanted pump 14. In FIG. 10A, power management module 140 presents thecurrent power drawn by the motor driving pump 14 in watts (w), thecurrent throughput of the pump in liters per minute (I/min), and thecurrent angular velocity of the pump motor in revolutions per minute(rpm). FIG. 10B illustrates an example in which power management module140 presents a description of an alarm the module issues to a user ofcontrol and power source module 12, as well as instructions for remedialactions that may be performed by the user to take the control and powersource module out of the alarm state.

Referring to FIGS. 7A, 7B, and 9A-10B, power management module 140 notonly presents users of control and power source module 12 withestimations of the amount of charge remaining in removable battery 24and internal battery 80, but also provides an estimate of the amount oftime the batteries will continue to operate before requiring replacementor recharging. For example, in FIGS. 7A and 7B, power management module140 calculates the time remaining on the battery charges as two hoursand forty five minutes, which is presented by user interface 50 ondisplay 52 just below removable battery icon 200. In FIGS. 9A and 9B,power management module 140 calculates the time remaining on the batterycharges as forty five minutes, which is presented by user interface 50on display 52 just below removable battery icon 200. In one example,power management module 140 may calculate and user interface 50 maypresent the time remaining on the charge of removable battery 24. Inanother example, power management module 140 may calculate and userinterface 50 may present the time remaining on the charge of internalbattery 80. In another example, power management module 140 maycalculate and user interface 50 may present the total time remaining onthe charges of both removable battery 24 and internal battery 80. Inanother example, power management module 140 may calculate the timeremaining on the charges of each of removable battery 24 and internalbattery 80, which user interface may present separately on display 52.

Power management module 140 may use a number of different types ofestimations and/or assumptions to calculate time remaining on thebattery charges for control and power source module 12. In one example,power management module 140 may assume a default nominal power draw fromthe components of control and power source module 12 and implanted pump14 and calculate the time remaining on the battery charges based on thedefault power requirement and the amount of charge left on removablebattery 24 and internal battery 80. In another example, power managementmodule 140 may track and store the power drawn by the components ofcontrol and power source module 12 and implanted pump 14 and average thepower requirements over time. Power management module 140 may thencalculate the time remaining on the battery charges based on the averagehistorical power requirement and the amount of charge left on removablebattery 24 and internal battery 80.

Referring again to FIG. 5, in addition to the redundant power sourcearchitecture described above, control of control and power source module12 also includes dual processors 130, 132 and two telemetry modules 136,138, both which elements of the device of FIG. 5 may be configured forredundant and/or complementary operation. Control and power sourcemodule 12 may employ first and second processors 130, 132 to provideerror protection and redundant operation in the event one processormalfunctions. Additionally, first and second processors 130, 132 may beconfigured to power different components of control and power sourcemodule 12 and to further improve power management achieved by thedevice. In this sense, the use of first and second processors 130, 132may be controlled by power management module 140, which, as noted above,may, in some examples, be embodied as one or both of processors 130, 132and memory 134.

In one example employing error protection and redundancy techniques,first and second processors 130, 132 are configured to periodically testeach other to detect malfunctions and/or failures. In the event one offirst and second processors 130, 132 malfunctions or fails, the other ofthe processors may shut down the malfunctioning processor and assumemanagement/control of any of the components of control and power sourcemodule 12 and/or implanted pump 14 previously handled by themalfunctioning processor. Additionally, the one of first and secondprocessors 130, 132 that is still operating properly may trigger analarm to alert a user of control and power source module 12 to theprocessor error/failure. For example, the one of first and secondprocessors 130, 132 that is still operating properly may control display52 of user interface 50 to present a message to the user of control andpower source module 12, which the processor may retrieve, e.g., frommemory 134.

In addition to error protection and redundancy techniques, first andsecond processors 130, 132 may be configured to manage and controldifferent components of control and power source module 12 and one ofthe two may be configured to manage and control implanted pump 14. Inthe example of FIG. 5, first processor 130 is communicatively connectedto memory 134, first telemetry module 136, power management module 140,and speaker driver 150. Power management module 140, connected to andassociated with first processor 130, is communicatively connected tocharger 142, power junction 146, and power inverter 148. In the exampleof FIG. 5, therefore, first processor 130, by default, is configured tocontrol and manage implanted pump 14 via power management module 140 andpower inverter 148. Second processor 132, on the other hand, isconnected to memory 134, second telemetry module 138, sensors 152, anduser interface 50. Thus, the control and management of control and powersource module 12 is split between first processor 130 and secondprocessor 132. The connection lines illustrated between components ofcontrol and power source module 12 in FIG. 5 are not meant to representthe only connections in the device. For example, in the event that firstprocessor 130 malfunctions or fails, second processor 132 may take overcontrol and management of implanted pump 14 via power management module140 and power bridge 148.

In order to provide redundant operation of implanted pump controller 21,both first and second processors 130, 132 are configured to control andmanage the power transfer in the event the other processor malfunctionsor fails. However, first and second processors 130, 132 may not be, insome examples, exactly the same. For example, one of first and secondprocessors 130, 132 may have lower power requirements than the otherprocessor to further decrease the power loads on removable batter 24 andinternal battery 80 of control and power source module 12. In any event,splitting the control and management of control and power source module12 between first processor 130 and second processor 132 enables some ofthe components of the device to be shut down when not in use, which may,in turn, significantly decrease the power requirement of the electronicsof the device. Thus, although control and power source module 12 may bedesigned to maximize space utilization and minimize the size of thedevice and although two processors may take up more space and weighsmore than one, employing first and second processors 130, 132 mayeffectively reduce the power requirements enough that the size andcapacity of removable battery 24 and internal battery 80 are alsoreduced.

In one example, first processor 130 is configured to transfer power andcommunicate to pump controller 21 via power bridge 148, first telemetrymodule 136, power management module 140, and also to control speakerdriver 150. Second processor 132 is configured to control user interface50, second telemetry module 138, and sensors 152. However, only alimited number of these components of control and power source module 12are required be running all or even most of the time, which areprimarily those affecting or relating to operation of power transfer andcommunications to pump controller 21. As such, first processor 130 andsecond processor 132 may be configured to shut down one or more of thecomponents they control in the event they are not in use. For example,second processor 132 may be configured to shut down user interface 50and second telemetry module 138 when these components of control andpower source module 12 are not in use. Additionally, in this example,second processor 132 does not control any components related toimplanted pump controller 21 or any other component that must operateuninterrupted. As such, second processor 132 may be shut down. In suchexamples in which second processor 132 is shut down, in the event acomponent controlled by the processor needs to operate, e.g. a usercalls on an element of user interface 50, first processor 130 may beconfigured to detect this activity and wake-up second processor 132.Additionally, in order to continue to provide error protection andredundancy, first processor 130 may be configured to periodicallywake-up second processor 132, which, in turn, may then check the firstprocessor for any malfunctions or failures. In another example, secondprocessor 132 may be configured to periodically wake itself up to testfirst processor 130 for errors or failures.

In accordance with foregoing example split of control between first andsecond processors 130, 132, first processor 130 may store data on andretrieve data from memory 134 related to the operation of pumpcontroller 21 and pump 14, as well as, e.g., speakers 90. In particular,first processor 130 may, e.g., retrieve information stored on memory 134related to parameters for controlling pump 14 to pump blood throughheart 30 of patient 20. In some examples, pump 14 may include anelectric motor that drives operation of the pump to draw blood from leftventricle 36 and deliver it to aorta 38. For example, pump 14 mayinclude any number of types of three-phase direct current (DC) oralternating current (AC) motors that are controlled by implanted pumpcontroller 21 using parameters received from first processor 130including, e.g., motor speed (RPM) and power range (nominal, high, maxpower in Watts), retrieved from memory 134.

First processor 130 may also receive feedback from pump controller 21 orother devices including, e.g., removable battery 24 and internal battery80 and store data related to the operation of the devices on memory 134.In another example, first processor 130, e.g. as part of powermanagement module 140 monitors the level of charge in each of removablebattery 24 and internal battery 80 and controls status user interface 50to indicate to patient 20 how much charge remains in each battery, e.g.graphically on display 52.

In another example, one or more of the foregoing functions related tothe operation of implanted pump 14 may be executed by second processor132. For example, in the event first processor 130 malfunctions orfails, second processor 132 may be configured to take over powertransfer to implanted pump controller 21.

Memory 134 of control and power source module 12 is a computer-readablestorage medium that may be used to store data including instructions forexecution by first and second processors 130, 132 or a processor ofanother device, such as, but not limited to, data related to theoperation of pump 14 to assist heart 30 of patient 20. In anotherexample, memory 134 may store data related to power management functionsexecuted by power management module 140. In another example, memory 134may store data related to power transfer functions executed by powerinverter 148. For example, memory 134 may store threshold charge levelvalues associated with different threshold charge levels for one or bothof removable battery 24 and internal battery 80. In one example, memory134 stores the low and empty threshold charge levels employed in thepower management state diagram of FIG. 6. Memory 134 may includeseparate memories for storing instructions, patient information, pump orpump motor parameters (e.g., motor speed and power range), patient andpump operation histories, and other categories of information such asany other data that may benefit from separate physical memory modules.In some examples, memory 134 stores data that, when executed by first orsecond processor 130, 132, cause control and power source module 12 andpump 14 to perform the functions attributed to them in this disclosure.

Components described as processors within control and power sourcemodule 12, e.g. first and processors 130, 132 or any other devicedescribed in this disclosure may each include one or more processors,such as one or more microprocessors, digital signal processors (DSPs),application specific integrated circuits (ASICs), field programmablegate arrays (FPGAs), programmable logic circuitry, or the like, eitheralone or in any suitable combination. Additionally, memory 62 and othercomputer readable storage media described in this disclosure may includea variety of types of volatile and non-volatile memory including, e.g.,random access memory (RAM), static random access memory (SRAM), readonly memory (ROM), programmable read only memory (PROM), erasableprogrammable read only memory (EPROM), electronically erasableprogrammable read only memory (EEPROM), flash memory, a hard disk,magnetic media, optical media, or other computer readable media.

In addition to first and second processors 130, 132 and memory 134,control and power source module 12 includes first and second telemetrymodules 136, 138. Generally speaking, first telemetry module 136facilitate wireless communications from and to control and power sourcemodule 12 and implanted pump controller 21. Generally speaking, secondtelemetry modules 138 facilitate wireless communications from and tocontrol and power source module 12 and other devices including, e.g. aseparate display device for presenting a user interface to patient 20 oranother user like a clinician or an device implanted within the patient,e.g. an implanted physiological sensor. First and second telemetrymodules 136, 138 in control and power source module 12, as well astelemetry modules in other devices described in this disclosure, can beconfigured to use a variety of wireless communication techniques,including, e.g. RF communication techniques to wirelessly send andreceive information to and from other devices respectively. First andsecond telemetry modules 136, 138 may, e.g., employ RF communicationaccording to one of the 802.11, a Medical Implant Communication Service(MICS), Bluetooth or Bluetooth Low Energy specification sets, infrared(IR) communication according to the IRDA specification set, or anotherstandard or proprietary telemetry protocol. First and second telemetrymodules 136, 138 may send information from and receive information tocontrol and power source module 12 on a continuous basis, at periodicintervals, or upon request from a user, e.g. patient 20 via a userinterface device. In one example, second telemetry modules 138communicates with a separate user interface device that includes adisplay, e.g. a liquid crystal display device (LCD) to display topatient 20 or another user the operation status of control and powersource module 12, implanted pump controller 21, and pump 14, as well asthe specific status of removable battery 24 and internal battery 80.

In one example of control and power source module 12, power may bedelivered unregulated from removable battery 24 or internal battery 80,e.g. via a switch to driver 150 and speakers 90. In contrast to theoperation of a component such as speakers 90, however, power managementmodule 140 may manage power delivered from removable battery 24 orinternal battery 80 through connector 26 and cable 18 to the primaryresonant network 15, using power inverter 148. In one example, firstprocessor 130 may control power bridge 148, which may include circuitryfor properly and safely delivering power to internal pump controller 21.

FIG. 11 is a circuit diagram illustrating the circuitry of powerjunction 146 (FIG. 5) in more detail. As seen in FIG. 11, power junction146 includes power mux circuitry, shown generally at 500, and chargerswitches circuitry, shown generally at 502. As described in more detailbelow, power mux circuitry 500 allows power from several power sources,i.e., a power adapter, removable battery 24, and internal battery 80, tobe combined and delivering power from only a single power source to thepower inverter 148.

In accordance with this disclosure, power mux circuitry 500 is designedto allow the highest voltage between the power sources, i.e., a poweradapter, the removable battery, and the internal battery, to be selectedand thus power the pump motor. As seen in FIG. 11, adapter voltage rail504 is connected to Schottky diode 506, removable battery voltage rail508 is connected to FET 510, and internal battery voltage rail 512 isconnected to FET 514. The cathode of diode 506 and the drain of FET 510are connected at a first terminal of charger sense resistor 516 and thedrain of FET 514 is connected to a second terminal of sense resistor516. Each of FETs 510, 514 is controlled by a FET controller, namely FETcontrollers 518, 520, respectively, to keep FETs 510, 514 operating atpeak efficiency. One example FET controller that may be used to controlFETs 518, 520 is an LM5050-2, available from National Semiconductor.

Each of FETs 518, 520 behave like ideal diodes, thereby effectivelycreating three “OR”-ing diodes. Whichever of the three voltages rails,i.e., adapter voltage rail 504, removable battery voltage rail 508, andinternal battery voltage rail 512, is highest will appear at the commonnode between the three, i.e., sense resistor 516. For example, removablebattery voltage rail 508 and internal battery voltage rail 512 may eachhave a maximum voltage of 16.8 Volts (V) and adapter voltage rail 504may have a maximum voltage of 18V. Whenever an adapter is connected to acontrol and power source module, e.g., control and power source module12, the adapter voltage will always be selected as the voltage to powerthe pump motor via motor bus 522 (an unregulated high voltage rail tothe pump). That is, adapter voltage rail 504 will be reduced by about0.2-0.3V by Schottky diode 506 to a voltage of about 17.7-17.8V, and theremovable battery voltage rail 508 and internal battery voltage rail 512will be reduced to a voltage of about 16.1-16.2V due to the ideal diodedrop (0.6V-0.7V) of FETs 510, 514. It should be noted that the adaptervoltage (either AC or DC) is designed to be higher than either theremovable or internal battery voltages so that power mux circuitry 500automatically defaults to the adapter as the power supply to motor bus522.

Still referring to power mux circuitry 500, internal battery voltagerail 512 is also connected to FET 524. FET 524 acts as a switch and isincluded in power mux circuitry 500 to allow the internal battery to beconnected and disconnected. In addition, if not for FET 524, theinternal battery and the removable battery would drain at the samevoltage level.

To the left of FET 524 in FIG. 11, logic circuitry is included tocontrol the operation of FET 524. Generally, the removable batteryvoltage rail, shown at 526, is fed into comparator 528, which includes a1.25V internal reference voltage. The output of comparator 528 is fedinto 3-input OR-AND gate 530 along with two internal battery signals,532, 534. In particular, the output of comparator 528 is fed along withinternal battery signal 532 from a pump processor, e.g. first processor130 of control and power source module 12 of FIG. 5, into the OR portionof OR-AND gate 530, and internal battery signal 534 from a UI processor,e.g. second processor 132 of control and power source module 12 of FIG.5, is fed along with the output of the OR portion into the AND portionof OR-AND gate 530. In this manner, the operation of FET 524, and thuswhether the internal battery is connected to the control and powersource module, may be controlled (via inverter gate 536 and FET 538).For example, as a safety feature, if there is no removable batteryvoltage, then both the pump processor and the UI processor must agreeand generate control signals in order for the system to shut off FET 524(and thus disconnect the internal battery from the circuit and thecontrol and power source module).

As another safety feature, a sudden drop in the removable batteryvoltage will turn FET 524 ON, thereby connecting the internal battery tothe control and power source module. In particular, comparator 528compares the removable battery voltage to its internal reference andprovides an output, e.g., a logical low, to the OR portion of OR-ANDgate 530. The output of the OR portion is fed along with internalbattery signal 534, e.g., a logical low, into the AND-portion of OR-ANDgate 530, which then turns on FET 524 via inverter gate 536 and FET 538,thereby connecting the internal battery to the control and power sourcemodule.

In other examples, FET 524 may be automatically controlled based on loaddemands. For example, during power up, the pump motor may draw morepower than during a steady state condition. Using the techniquesdescribed above, power mux circuitry 500 may automatically switch overfrom the removable battery to the more power-dense internal batteryuntil the pump motor reaches a steady state condition. In operation, ifthe removable battery cannot sustain the load, then removable batteryvoltage rail 526 temporarily collapses, resulting in comparator 528firing, thereby turning on FET 524 and connecting the internal batteryvoltage rail 508 to motor bus 522.

In some examples, the pump processor may control FET 524 during pumpstart up by outputting specific control signals. It may be desirable forthe first processor to control FET 524 during start up because allowingthe removable battery voltage to temporarily collapse may generateunnecessary heat. In addition to start up, physiological conditions maycause the pump motor to work harder and thus increase the load. Forexample, certain medications may result in thickening of the blood, andcertain activities, such as lifting heavy objects, may causevasoconstriction. In either case, the pump may need to work harder and,as a result, draw more power from the power source. Using the techniquesdescribed above, an alternate power source may be used to accommodateincreased demand from the pump.

It should be noted that in order to save power, the second processor maybe configured to shut off if no services are being provided. The secondprocessor may periodically wake up, e.g., once every second, to verifythat the first processor is working properly, thereby providing across-checking function. In some examples, the first processor may senda signal to the second processor, e.g., via a serial peripheralinterface (SPI) bus, and receives a predictable response. FIG. 12 is acircuit diagram illustrating the circuitry of charger 142 (FIG. 5) inmore detail. In FIG. 12, charger circuitry 600, via battery charger 602,provides dynamic power management, which provides less power to thebattery if the system is requiring more power so that the system is notstarved of power. Using the techniques of this disclosure, chargercircuitry 600 may change the power system limit based on the batteryfrom which the system is drawing power.

As mentioned above and as seen in FIG. 11, both external power sources,i.e., the adapter and the removable battery, are connected to senseresistor 516. Battery charger 602 measures how much power is coming into the system and battery charger 602 knows how much power it isproviding to the removable battery during charging. Using dynamic powermanagement, charger circuitry 600 may change the power system limitbased on the battery from which the system is drawing power in order toprovide less power to the battery during charging so that the system isnot deprived of power. The power system limit is how much power thesystem needs and, in accordance with this disclosure, is settable. Inparticular, charger circuitry 600 includes FET 604 and a resistordivider network, shown generally at 606. Based on whether the systemneeds more power or less power, the pump processor controls FET 604 toturn ON or OFF, thereby switching in or switching out a leg of resistordivider network 606. In some example implementations, the power systemlimit may be controlled via a digital-analog converter (DAC) output.

In addition, in accordance with this disclosure, sense resistor 516(FIG. 11) is connected to the external power sources, namely the adapterand the removable battery, and not the internal battery. Sense resistor516 need not be connected to the internal battery because, by design,the system does not charge from the internal battery.

Further, charger circuitry 600 includes resettable fuse 606 for safety.It should be noted that resettable fuse 606 may be included on thecharger board in some example implementations.

Referring again to FIG. 11, charger switches circuitry 502 provides afail-safe means to control whether the internal battery or the removablebattery receives power from the charger, thereby allowing the system touse a single charger circuit. Charger switches circuitry 502 includes acombination of FETs and logic circuitry that allows the pump processorto select which battery is charging. The logic circuitry eliminates thepossibility of a short between the internal and removable batteries.

In charger switches circuitry 502, the pump processor provides twocontrol signals, namely internal battery switch signal 608 and removablebattery switch signal 610, to exclusive-OR gate 612. The output ofexclusive-OR gate 612 is fed into one input of each of the AND gates ofa dual 2-input positive AND gate, shown generally at 614. The other twoinputs of the AND gates of dual 2-input AND gate 614 are supplied byinternal battery switch signal 608 and removable battery switch signal610. In particular, internal battery switch signal 608 is supplied to aninput of AND gate 616 and removable battery switch signal 610 issupplied to an input of AND gate 618. The output of AND gate 616 turnson FET 620, which causes the internal battery to begin charging throughFETs 624 and 626. The output of AND gate 618 turns on FET 622, whichcauses the removable battery to begin charging through FETs 628 and 630.

In one example implementation, the removable battery begins charging ifinternal battery switch signal 608 is a logic level low and removablebattery switch signal 610 is a logic level high, and the internalbattery begins charging if internal battery switch signal 608 is a logiclevel high and removable battery switch signal 610 is a logic level low.If internal battery switch signal 608 and removable battery switchsignal 610 are at the same logic level (low or high), then neitherbattery is charging.

FIGS. 13A and 13B are plan and elevation views, respectively, ofremovable battery 24 and battery release latch 700 for use with acontrol and power source module according to this disclosure, e.g.control and power source module 12 of FIGS. 2A-4B. Although only onebattery release latch 700 is illustrated in the FIG. 13A, a secondsimilarly configured battery release latch may be arranged on theopposite side of the control and power source module such that bothlatches may be engaged to release removable battery 24. In the exampleof FIGS. 13A and 13B, battery release latch 700 includes push button702, catch 704, pivot 706, and spring return 708. Removable battery 24includes stop 710 configured to engage catch 704 on battery releaselatch 700 to lock the battery in housing 22 of control and power sourcemodule 12.

In FIGS. 13A and 13B, push button 702 and catch 704 of battery releaselatch 700 are connected and pivot about pivot 706. Spring return 708 isarranged to abut and engage push button 702 to bias the battery leaselatch 700 such that catch 704 pivots about pivot 706 to engage stop 710on removable battery 24. To release removable battery 24, a user maypush on push button 702, causing push button 702 and catch 704 to pivotabout pivot 706 such that catch 704 moves out of engagement with stop710 on removable battery 24. Removable battery 24 may be manuallyremoved by the user after unlatching battery release latch 700 orcontrol and power source module 12 may include automatic eject mechanismthat ejects the battery at least partially out of housing 22 when thelatch is no longer engaging the battery.

FIGS. 14A and 14B are broken plan and elevation views, respectively, ofremovable battery 24 and another type of battery release latch 800 foruse with a control and power source module according to this disclosure,e.g. control and power source module 12 of FIGS. 2A-4B. FIGS. 14C and14D are section views cut along section line A-A of FIG. 14Aillustrating two different examples of battery release latch 800.Although only one battery release latch 800 is illustrated in the FIGS.14A-14D, a second similarly configured battery release latch may bearranged on the opposite side of the control and power source modulesuch that both latches may be engaged to release removable battery 24.In FIGS. 14A and 14B, battery release latch 800 is integral withremovable battery 24 and configured with push buttons that may pivotabout the X-axis (horizontal in the view of FIG. 14A) or the Y-axis(vertical in the view of FIGS. 14A and 14B). The examples illustrated inFIGS. 14C and 14D both include push buttons configured to pivot aboutaxis Y. However, in other examples, a battery release latch may beconfigured in accordance with the examples of FIGS. 14C and 14D with thepush buttons pivoting about the X-axis.

In the example of FIG. 14C, battery release latch 800A integral withremovable battery 24 includes push button 802, catch 804, and resilienttab 806. Housing 22 includes stop 808 configured to engage catch 804 onbattery release latch 800A to lock the battery in housing 22 of thecontrol and power source module. Push button 802 and catch 804 ofbattery release latch 800A are configured to rotate at resilient tab806. Resilient tab 806 may, in one example, be formed from a resilientmaterial that biases battery lease latch 800A such that catch 804 pivotsabout resilient tab 806 to engage stop 808 on housing 22. To releaseremovable battery 24, a user may push on push button 80, causingresilient tab 806 to flex, which permits push button 802 and catch 804to pivot about resilient tab 806 such that catch 804 moves out ofengagement with stop 808 on housing 22. Removable battery 24 may bemanually removed by the user after unlatching battery release latch 800Aor the control and power source module may include an automatic ejectmechanism that ejects the battery at least partially out of housing 22when the latch is no longer engaging the battery.

In the example of FIG. 14D, battery release latch 800B integral withremovable battery 24 includes push button 802, catch 804, pivot 810, andspring return 812. In this example, push button 802 and catch 804 ofbattery release latch 800A are configured to rotate about pivot 810.Spring return 812 is arranged to abut and engage push button 802 to biasthe battery lease latch 800A such that catch 804 pivots about pivot 810to engage stop 808 on housing 22. To release removable battery 24, auser may push on push button 80, compressing spring return 812 andcausing push button 802 and catch 804 to pivot about pivot 810 such thatcatch 804 moves out of engagement with stop 808 on housing 22. Removablebattery 24 may be manually removed by the user after unlatching batteryrelease latch 800B or the control and power source module may include anautomatic eject mechanism that ejects the battery at least partially outof housing 22 when the latch is no longer engaging the battery.

Wireless Power Transfer System

FIG. 15 is a block diagram of the wireless power transfer system 11shown in FIG. 1. The system 11 may be referred to as a transcutaneousenergy transfer system (TETS) when applied to implantable electronicapplications. The system 11 has an external assembly 1504 that isprovided at an external location outside of a subject and an internalassembly 1508 that is implanted within the subject. The internalassembly includes an implantable medical device. The implantable medicaldevice may be any medical device capable of being implanted in asubject, such as a heart pump, an artificial heart, a right ventricleassist device, a left ventricle assist device, a BIVAD, a minimallyinvasive circulatory support system, a cardiac pace maker, and so on.While the implanted device may be any implantable medical device, thisdisclosure describes the transcutaneous energy transfer system 11 in thecontext of a heart pump 14 by way of example and not limitation.

As shown in FIG. 15, the external assembly 1504 may include the externalresonant network 15. Similarly, the internal assembly 1508 may includethe internal resonant network 17. The external assembly 1504 and theinternal assembly 1508 are also shown in FIG. 16A, which is a circuitdiagram that includes certain components of the transcutaneous energytransfer system 11. The external resonant network 15 may include anexternal coupler in the form of an inductive coil 1648 and a capacitor1652 connected in series. Similarly, the internal resonant network 17may include an internal coupler in the form of an inductive coil 1656and a capacitor 1660 connected in series. As shown in FIG. 16A, theexternal resonant 15 may be configured such that the inductive coil 1648is connected directly to the inverter 148 through the capacitor 1652. Itshould be appreciated that the series-series topology illustrated inFIG. 16A is shown by way of example and not limitation. Alternativeembodiments may be used that employ different circuit topologies, suchas series-parallel, parallel-series, parallel-parallel and so on.

FIGS. 16B-C are circuit diagrams of embodiments of the transcutaneousenergy transfer system 11 that include an external resonant network 15having a variable transformer topology. Like the embodiment shown inFIG. 16A, the external resonant network 15 of FIGS. 16B-C includes aninductive coil 1648 and a capacitor 1652 and is provided in associationwith an internal resonant network 17 having a coil 1656 and a capacitor1660. Unlike the embodiment shown in FIG. 16A, the inductive coil 1648in FIGS. 16B-16C is not directly connected to the inverter 148. Rather,the inductive coil 1648 forms a portion of a variable transformersection 1676. The variable transformer section 1676 is arranged on thesecondary side of a transformer 1680, which, in turn, is connected tothe inverter 148. The transformer 1680 may be a corded transformer thatincludes an iron or ferrite core that supports primary and secondarywindings. The transformer 1680 may include a coil 1684 that forms theprimary transformer winding. The coil 1684 may be connected to theinverter 148 through the capacitor 1652. The transformer 1680 mayconnect to the variable transformer section 1676 through a plurality ofcoils 1688 that form a plurality of secondary transformer windings.

The variable transformer section 1676 includes a plurality oftransformer legs 1692 arranged in parallel. By way of example and notlimitation, FIG. 16B shows a variable transformer section 1676 havingtwo transformer legs 1692. The variable transformer section 1676 mayinclude greater numbers of transformer legs 1692 in otherimplementations. Thus, FIG. 16C shows a variable transformer section1676 having an arbitrary number n of transformer legs 1692. As shown inFIG. 16B-C, each transformer leg 1692 may include one of the pluralityof coils 1688 that form the plurality of secondary windings of the coredtransformer 1680. Within each of the transformer legs 1692, the coil1688 is connected to a capacitor 1696 so as to form a resonant circuitcomponent. Additionally, each transformer leg 1692 is connected to theinductive coil 1648 through a switch 1698. Each of the switches 1698 maybe separately and independently actuated so as to switch thecorresponding transformer legs 1692 in and out of the variabletransformer section 1676. In this way, the behavior of the externalresonant network 15 may be adjusted responsive to changes in powerand/or coupling needs that arise during the operation of transcutaneousenergy transfer system 11.

FIGS. 17A and 17B are schematic illustrations of the internal 1656 andexternal 1648 coils. In FIG. 17A, the internal coil 1656 is disposedbeneath the skin 1664 of a subject, and the external coil 1648 isdisposed generally adjacent the internal coil 1656. In FIG. 17B, theinternal coil 1656 is disposed beneath the skin 1664 of a subject, andthe external coil 1648 is disposed at some distance from the internalcoil 1656. As shown in FIGS. 17A and 17B, the internal coil 1656 mayhave a plurality of conductive windings 1704 disposed in a circularinsulating member 1708. Similarly, the external coil 1648 may have aplurality of conductive windings 1712 disposed in an insulating ring1716. The inductance of each of the coils 1656, 1648 may be determinedby the number, diameter and spacing of the windings 1704, 1712. Theinductive or electromagnetic coupling between the coils 1648, 1656 is afunction of their physical proximity, operating frequencies, coil sizes,and inductances. While the coils shown in FIGS. 17A and 17B have agenerally circular shape, other shapes and structures may be used toimplement the internal 1656 and external 1648 coils, depending on theimplementation. For example, the coils 1648, 1656 may be shaped as atriangle, square, rectangle, pentagon, octagon, and so on. Generally,the coils 1648, 1656 may be shaped as polygons of any number of sides,which may be equal or unequal in length. The coils may be straight incertain portions and/or curved in certain portions. The coils 1648, 1656may be arranged in a planar configuration. Alternatively, the coils1648, 1656 may be arranged such that portions of the coils lie indifferent planes.

The coils 1648, 1656 together constitute a loosely coupled transformer,with the external coil 1648 acting as a primary winding and the internalcoil 1656 acting as a secondary winding. The coils 1648, 1656 and thecapacitors 1652, 1660 with which they may be connected may form aresonant circuit. The coils 1648, 1656 may be tuned to the same ordifferent resonant frequencies. For example, the coils 1648, 1656 may beseries tuned to a power transmission frequency of about 200 kHz. Theexternal coil 1648 may induce an electric current in the internal coil1656, which current generally behaves in accordance with the followingequation:

$\begin{matrix}{\frac{V_{1}}{I_{2}} = {\frac{V_{2}}{I_{1}} = {\omega \cdot k \cdot \sqrt{L_{1} \cdot L_{2}}}}} & (1)\end{matrix}$

In Equation (1), I₁ is the current induced in the external resonantnetwork 15. I₂ is the current induced in the internal coil network 17.V₁ is the voltage across the external resonant network 15. V₂ is thevoltage across the internal resonant network 17. ω is the frequency ofthe voltage across the coils 1648, 1656, where the coil networks aretuned to the same frequency ω. L₁ is the inductance of the external coil1648. L₂ is the inductance of the internal coil 1656. k is the couplingcoefficient.

The external assembly 1504 is located on the outside of the skin 1664 ofthe subject and includes the external coil network 15. The externalassembly 1504 additionally includes the control and power source module12, which is generally illustrated in FIG. 1. As shown in FIG. 5, thecontrol and power source module 12 includes various components includingthe battery 24, the first processor 130, and the power inverter 148.These components each have a role in wireless power transfer system 11and as such are again illustrated in FIGS. 15, 16 and 18. Othercomponents of the control and power source module 12 portion of theexternal assembly 1504 are omitted from FIGS. 15, 16 and 18 for clarity.

Referring to FIGS. 15 and 16A-C, the external assembly 1504 includes thepower supply 24, which generally provides power in the form of a DCvoltage. In some embodiments, the power supply 24 is a portable batteryor battery pack providing a DC voltage of between 10 and 18 volts. Theexternal assembly 1504 also includes the power inverter 148, which maybe connected to the power junction 146 via a pair of conductive lines1604, 1608. The power junction 146 supplies the DC power from aplurality of possible sources including batteries 24 or 80 or anexternal DC power supply to the power inverter 148, which converts theDC voltage into a high-frequency voltage. The high-frequency voltage isprovided to the external resonant network 15 via a pair of conductors1612, 1616. A current sensor 1620 may be used to sense the electriccurrent flowing within the conductor 1616. The current sensor 1620 maybe configured to sense either or both of the magnitude and phase of theelectric current in the conductor 1616. The first processor 130 may beconnected to the current sensor 1620 via a conductor 1624 and may beused to control the operation of the power bridge 148, based on one ormore characteristics of the current sensed by the sensor 1620. The firstprocessor 130 may also be configured to control the voltage V_(in) thatis provided by the power junction 146. The external coil network 15,which is disposed adjacent the skin 1664 of the subject, transferselectric power through the skin 1664 of the subject to the internal coilnetwork 17 disposed beneath the skin 1664 of the subject.

The internal assembly 1508 is disposed beneath the skin 1664 of thesubject and includes the internal coil network 17. The internal assembly1508 additionally includes the internal controller module 21, which isgenerally illustrated in FIG. 1. As mentioned, the internal controllermodule 21 is generally configured to manage a power transfer that occursacross the external 15 and internal 17 resonant networks and to providepower to the implanted pump 14. The internal controller module 21includes various components such as a power circuit and a rectifier thatare illustrated in greater detail in FIGS. 15 and 16. Thus, as shown inFIG. 15, the internal coil network 17 is connected to a power circuit1532 via a pair of conductors 1628, 1632. The power circuit 1532includes a rectifier 1652 that performs full wave rectification of thesinusoidal AC current induced in the internal coil 1656 by the externalcoil 1648.

In one embodiment, the rectifier 1652 includes four switching elements,which may be provided in the form of diodes or Schottky diodes. During afirst half of the AC power cycle, a first pair of diodes provides aconductive path up from ground, through the internal coil 1656, and outto conductor line 1628. During a second half of the AC power cycle, asecond pair of diodes provides a conductive path up from ground, throughthe internal coil 1656, and out to conductor line 1628. In this way, therectifier 1652 converts AC power provided by the internal coil network17 into DC power that can be used by various components of the internalassembly 1508.

The power circuit 1532 additionally includes a regulator 1556 thatregulates power supplied by the rectifier 1652. The regulator 1556supplies electric power to a controller 1536 and other elements via apair of conductors 1640, 1644. The controller 1536 may control theoperation of the heart pump 14. The power conductors 1640, 1644 alsosupply electric power to a motor inverter that supplies power to theheart pump 14 through the controller 1536. The regulator 1556 may be ashunt type regulator that repeatedly charges and discharges a powersupply capacitor. In other implementations, other types of regulators,such as a series regulator, may be used. In one embodiment, the powersupply capacitor is a component of the charging circuit 1544. Thevoltage across the power capacitor is output via the lines 1640, 1644 tothe controller 1536 and may be inverted to supply power to the implantedmedical device such as heart pump 14.

During operation, the motor controller 1536 drives the heart pump 14 topump blood through the artificial heart assembly, drawing electriccurrent from the power supply capacitor associated with the chargingcircuit 1544. As current is drawn from the capacitor, the voltage acrossthe capacitor decreases. To replenish the voltage on the capacitor, thepower circuit 1532 periodically operates in a power supply mode in whichelectric current generated by the rectifier 1652 is provided to thecapacitor via the lines 1640, 1644. When not operating in the powersupply mode, the power circuit 1532 operates in an idle mode in whichcurrent is not supplied to the capacitor.

In the case of shunt type regulator 1556 shorting of the resonantsecondary 17 may be accomplished by one or more shorting switches 1672that operate to shift the power circuit 1532 between the power supplymode and the idle mode. In the power supply mode, the shorting switches1672 open to allow current to flow from the internal resonant network17, through the rectifier 1652, and out to the conductor line 1640/1644.In idle mode, the shorting switches 1672 close to short internalresonant network 17 so that current flows only within resonant network228 rather than out to the conductor lines 1640/1644.

The magnitude of the output voltage across the power supply capacitorassociated with regulator circuit 1556 may control whether the shortingswitches 1672 are open or closed and thus whether the power circuit 1532operates in the power supply mode or in the idle mode. For example, ifthe output voltage falls below a certain value, the shorting switches1672 open and the power circuit 1532 operates in the power supply mode.When the output voltage rises to a certain value, the shorting switches1672 close and the power supply circuit 1532 operates in the idle mode.By selectively supplying current to the power supply capacitor onlyduring certain times (i.e. the power supply mode), the voltage acrossthe capacitor is regulated, or maintained within a predetermined voltagerange, such as between about 13 and about 14 volts, for example.

In one embodiment, the shorting switches 1672 are implemented as a pairof switching transistors, such as field-effect transistors, though anysuitable structure may be used. For example, the shorting switches 1672may be implemented using bipolar junction transistors, and so on. Theswitching transistors may be configured to short diodes associated withthe rectifier 1652 in a conductive state and to not do so in anon-conductive state. A switching control circuit may control theconductive state of the switching transistors based on the outputvoltage across the power supply capacitor associated with the regulatorcircuit 1556. When the output voltage is above a certain value, thecontrol circuit turns on the switching transistors to short diodesassociated with the rectifier 1652. Here, current flows through theinternal resonant network 17 and through the conductive transistors.When the output voltage is below a certain value, the control circuitturns off the switching transistors so that the diodes associated withthe rectifier 1652 are not shorted. Here, current is allowed to flowfrom the internal resonant network 17, through the rectifier 1652, andout to the conductor line 1640/1644.

The external assembly 1504 may be responsive to the internal assemblyshifting between the power supply mode and the idle mode. As mentionedabove, the external assembly includes a first processer 130 that may beused to control the operation of the power inverter 148 based on one ormore characteristics of the current sensed by the sensor 1620. In thisregard, the power first processor 130 may change the frequency at whichthe power inverter 148 operates to conserve electric power during theidle mode. During the idle mode, when electric current is not beingsupplied to the capacitor associated with the charging circuit 1544, thepower transmitted to the internal coil 1656 by the external coil 1648 isreduced in order to conserve power. This is accomplished by changing thefrequency at which the power inverter 148 operates.

As noted above, the internal and external coils 1648, 1656 may be tunedto a power transmission frequency, such as about 200 kHz. Consequently,when it is desired to transmit power to the internal coil 1656, thepower inverter 148 is operated at the power transmission frequency towhich it is tuned. However, when it is not necessary to transmit asignificant amount of power, such as during the idle mode above, thefrequency of the power inverter 148 is changed. The frequency at whichthe power inverter 148 operates during the power-supply mode may bechanged to an odd sub-harmonic of that frequency during the idle mode.For example, the idle mode frequency may be ⅓, ⅕, 1/7, 1/9 of the powersupply mode frequency. The amount of power transmitted to the internalcoil 1656 varies with the idle mode frequency, with less power beingtransmitted at the seventh subharmonic (i.e. 1/7 of the power supplymode frequency, or 28.6 kHz if the power transmission frequency is 200kHz) than at the third subharmonic (i.e. ⅓ of the power supply modefrequency). Since odd subharmonics of a fundamental frequency stillcontain, in accordance with Fourier analysis, some components of thefundamental frequency, using an odd subharmonic of the power supply modefrequency during idle mode will still result in some power beingtransmitted to the internal coil 1656, which is generally desirable.

FIGS. 18A-C are circuit diagrams that show one implementation of theinverter 148. FIG. 18A corresponds to the circuit diagram of FIG. 16Awhere the inductive coil 1648 is connected directly to the inverter 148through the capacitor 1652. FIGS. 18B-C correspond to the circuitdiagrams of FIGS. 16B-C where the inductive coil 1648 forms a portion ofa variable transformer section 1676. As shown in FIG. 18A-C, the powerinverter 148 may comprise four transistors 1804, 1808, 1812, 1816, whichmay be metal oxide field-effect transistors (MOSFETs), connected in anH-bridge configuration. The four transistors 1804, 1808, 1812, 1816 maydrive the external coil network 15 through the conductor 1612. Each ofthe transistors 1804, 1808, 1812, 1816, may be controlled by arespective high-frequency drive signal provided on the conductor 1668,with two of the drive signals being 180° out of phase, or complemented,with respect to the other two via an inverter 1820. The drive signalsmay be 50% duty cycle square waves provided at a frequency of about 200kHz, for example. Although a particular type of DC-to-AC converter hasbeen described above, any type of electronic switching network thatgenerates a high-frequency voltage may be used. For example, as analternative to the H-bridge configuration, the power inverter 148 mayhave transistors arranged in a voltage source half bridge configurationor in a current source configuration or in a class-DE amplifier voltagesource configuration.

The power inverter 148 may be connected to the first processor 130 tocontrol the operation of the power inverter 148 based on one or morecharacteristics of the current sensed by the sensor 1620. Referring toFIGS. 16A-C, the power inverter 148 may be connected to the firstprocessor 130 through the conductor 1668. The first processor 130, inturn, may be connected to the current sensor 1620 via the line 1624.Referring to FIGS. 18A-C, first processor 130 may include certainpre-processing circuits 1824 that operate on the current signal and aprocessor 1826 that receives input generated by the pre-processingcircuit 1824 based on the current signal. The pre-processing circuits1824 may include circuits that accomplish such functions as current tovoltage conversion, decoupling detection, interference detection, andshorting/un-shorting detection, and so on.

In one embodiment, the pre-processing circuit 1824 may be configured togenerate a voltage that is indicative of the magnitude of the electriccurrent flowing through the external coil 1648, where the currentflowing through the external coil 1648 is proportional to the voltageacross the internal coil 1656. During the idle mode, the shortingswitches 1672 are closed, which causes the voltage across the internalcoil network 17 to significantly decrease. That voltage decrease causesthe current in the external coil 1648 to be significantly decreased, inaccordance with Equation (1). Consequently, the voltage generated by thepre-processing circuit 1824 decreases significantly when the powercircuit 1532 is in the idle mode.

The output of the first processor 130 may be configured to drive thepower inverter 148 at different frequencies depending on the voltagereceived from the pre-processing circuit 1824. In one embodiment, thepower management module 140 output may be provided by the processor1826, which provides output responsive to input from the pre-processingcircuit 1824. When the pre-processing circuit 1824 generates a voltagethat is not decreased indicating that the power circuit 1532 is in powersupply mode, the output of first processor 130 may drive the powerinverter 148 at a first frequency, such as 200 kHz. When thepre-processing circuit 1824 generates a voltage that is decreasedindicating that the power circuit 1532 is in idle mode, the output ofthe first processor 130 may drive the power bridge 148 at a secondfrequency that is an odd sub-harmonic of the frequency generated duringthe power supply mode.

FIGS. 18D-F are schematic diagrams of various implementations of theexternal assembly 1504. Each implementation includes at least anovercurrent detection circuit 1832 that protects the system fromexcessive current amounts. FIG. 18D shows an implementation, such as inFIG. 16A, where the external resonant network 15 is connected directlyto the inverter 148. FIG. 18E shows an implementation, such as in FIG.16B-C, where the external resonant network 15 is connected to theinverter 148 through a variable transformer section 1676. FIG. 18F showsan implementation that includes a variable voltage regulator 1836, whichmay be used to vary the voltage level of the input signal provided tothe inverter 148.

Each of the diagrams of FIGS. 18D-F includes a detailed illustration ofthe first processor 130. As mentioned, the first processor 130 mayinclude a processor 1826 that receives input from one or morepreprocessing circuits 1824. As shown in FIG. 18D-18F, the preprocessingcircuits 1824 may include a current sense and signal conditioningcircuit 1840. The current sense and signal conditioning circuit 1836 maybe configured to receive the output of the current sensor 1620 and toconvert this current signal to a voltage signal for use by the processor1826 and/or other preprocessing circuit 1824 components. Otherpreprocessing circuit 1824 components may include, for example, asecondary short detection circuit 1844, a decoupling detection circuit1848, and/or a phase detection circuit 1852.

The secondary short detection circuit 1844 may be configured to receivethe voltage signal generated by the current sense and signalconditioning circuit 1840. Based on this input signal, the secondaryshort detection circuit 1844 may generate a signal that indicates whenthe secondary resonant circuit is shorted or un-shorted. Morespecifically, the secondary short detection circuit 1844 may beconfigured to detect voltage levels that indicate whether the secondaryis operating in power supply mode or in idle mode. In response to theoutput provided by the short detection circuit 1844, the processor 1826may be configured to drive the inverter 148 at a power level thatmatches the power needs of the secondary.

The decoupling detection circuit 1848 may be configured to receive thevoltage signal generated by the current sense and signal conditioningcircuit 1840. Based on this input signal, the decoupling detectioncircuit 1848 may generate a signal that indicates when and to whatextent the primary and secondary are decoupled. In response to theoutput provided by the short detection circuit 1848, the processor 1826may be configured to take one or more actions to mitigate thedecoupling. Decoupling detection and calculation is discussed in greaterdetail below in connection with FIG. 21 and FIG. 22. Processor 1826actions that mitigate decoupling are discussed in connection with FIGS.24-37.

The phase detection circuit 1852 may be configured to receive thevoltage signal generated by the current sense and signal conditioningcircuit 1840. The phase detection circuit 1852 may additionally beconfigured to sense the voltage and/or current of the drive signal thatis provided to the inverter 148 by the processor 1826. If an interferingobject is present between the secondary and the primary, a phase shiftmay occur between these two input signals received at the phasedetection circuit 1852. The phase detection circuit 1852 may thus beconfigured to sense this phase difference and, in so doing, detect thepresence of the interfering object. This detection process is describedin greater detail below.

Scalable Power and Coupling Modes

The system 11 may be configured to shift between or among a number ofpower and/or coupling modes as power is transferred from the externalprimary to the implanted secondary. The system 11 may change powerand/or coupling modes through control inputs provided by the firstprocessor 130 or other appropriate components on the primary side of thesystem 11. As described above, the first processor 130 may be configuredto shift the power output by the primary side of the system 11 based oninput that indicates whether the power circuit 1532 on the secondaryside is operating in a power supply mode or in an idle mode. In additionto this functionality, the first processor 130 may also be configured toshift the system 11 into different scalable power and/or coupling modesbased on input such as data from communication channels, programmedtimers, and/or system monitoring parameters and calculations.

In some implementations, the system 11 may change power and/or couplingmodes through the operation of a variable transformer topology. Here,the system 11 may include a variable transformer section 1676, such asillustrated in FIGS. 16B-C and 18B-C. The first processor 130 may beconfigured to provide control inputs to the switches 1698, each of whichis associated with a particular leg 1692 of the variable transformersection 1676. By actuating the switches 1698, the first processor 130may operate to separately and independently switch the varioustransformer legs 1692 in and out of the variable transformer section1676. In so doing, the first processor 130 may shift the system 11between or among different power and/or coupling modes.

Thus, the system 11 may be configured for scalable power modes and thefirst processor 130 may shift the system 11 to deliver greater amountsof power by switching in additional transformer legs 1692. Similarly,the first processor 130 may shift the system 11 to deliver lesseramounts of power by switching out transformer legs 1692. Alternativelyor in combination, the system 11 may be configured for scalable couplingmodes and the first processor 130 may shift the system 11 to operatewith greater amounts of coupling by switching in additional transformerlegs 1692. Similarly, the first processor 130 may shift the system 11 tooperate with lesser amounts of coupling by switching out transformerlegs 1692.

The system 11 may also change power and/or coupling modes by switchingbetween or among different subharmonics of the power transmissionfrequency. As mentioned above, when the power circuit 1532 on thesecondary side is operating in idle mode, the first processor 130 maydrive the inverter 148 at an odd subharmonic of the power transmissionfrequency to which the coils 1648, 1656 are tuned. In addition to thisfunctionality, the first processor 130 may be configured to drive theinverter 148 at different subharmonics of the power transmissionfrequency so as to shift the system 11 between or among different powerand/or coupling modes.

FIG. 19 is a graph 1900 that illustrates different subharmonics of thepower transmission frequency for an example system 11. The graph 1900compares the power transmission frequency (shown on the x-axis) to thepower output as a fraction of power output at the fundamental (shown onthe y-axis). The graph 1900 includes the fundamental power transmissionfrequency 1904. As mentioned, the fundamental 1904 corresponds to thepower transmission frequency to which the coils 1648, 1656 are tuned. Byway of example and not limitation, the graph 1900 also includes twosubharmonics 1908, 1912 of the fundamental 1904. In accordance withembodiment discussed herein, the subharmonics 1908, 1912 correspond todifferent power or coupling modes of the system. In accordance withother implementations, the system 11 may operate at greater than twosubharmonics and thus have greater numbers of scalable power and/orcoupling modes.

Thus, the system 11 may be configured for scalable power modes and thefirst processor 130 may shift the system 11 to deliver greater amountsof power by switching the inverter 148 to operate at a highersubharmonic of the power transmission frequency. Similarly, the firstprocessor 130 may shift the system 11 to deliver lesser amounts of powerby switching the inverter 148 to operate at a lower subharmonic of thepower transmission frequency. Alternatively or in combination, thesystem 11 may be configured for scalable coupling modes and the firstprocessor 130 may shift the system 11 to operate with greater amounts ofcoupling by switching the inverter 148 to operate at a highersubharmonic of the power transmission frequency. Similarly, the firstprocessor 130 may shift the system 11 to operate with lesser amounts ofcoupling by switching the inverter 148 to operate at a lower subharmonicof the power transmission frequency.

The system 11 may also change power and/or coupling modes the throughthe operation of a phase shifted bridge controller. As described above,the inverter 148 may be implemented as a number of transistors arrangedin an H-bridge or other appropriate configuration. In a system thatimplements a phase shifted bridge controller, the input voltageamplitude in the resonant circuit is varied by changing the duty cycleof the square wave voltage out of the driver. In a full bridgeimplementation the duty cycle change is accomplished by shifting timingof the left half-bridge relative to the right half bridge, where innormal 50% duty cycle operation the left and right sides are alwayscomplimentary. In a half bridge implementation the duty cycle change isimplemented directly.

Thus, the system 11 may be configured for scalable power modes and thefirst processor 130 may shift the system 11 to deliver greater amountsof power by shifting the voltage and current signals produced by theinverter 148 to be more in phase. Similarly, the first processor 130 mayshift the system 11 to deliver lesser amounts of power by shifting thevoltage and current signals produced by the inverter 148 to be less inphase. Alternatively or in combination, the system 11 may be configuredfor scalable coupling modes and the first processor 130 may shift thesystem 11 to operate with greater amounts of coupling by shifting thevoltage and current signals produced by the inverter 148 to be more inphase. Similarly, the first processor 130 may shift the system 11 tooperate with lesser amounts of coupling by shifting the voltage andcurrent signals produced by the inverter 148 to be less in phase.

The system 11 may be configured for scalable power modes such that thesystem 11 can operate in a plurality of discrete power modes. The system11 may include any number of discrete power modes and the number ofdiscrete power modes can depend on the particular implementation. Forexample, the system 11 may include two discrete power modes, threediscrete power modes, four discrete power modes, and so on. The numberof discrete power modes in a particular system 11 may correspond to thenumber of different discrete configurations into which the system 11 maybe shifted. In a system 11 that implements a variable transformertopology, the number of discrete power modes may correspond to thenumber of different possible combinations of individual transformer legs1692 shifted in or out of the variable transformer section 1676. In asystem 11 that switches between or among different subharmonics of thepower transmission frequency, the number of discrete power modes maycorrespond to the number of different possible subharmonics on whichpower can be transferred. In a system 11 that implements a phase shiftedbridge controller, the number of discrete power modes may correspond tothe number of different possible phase shifts that can be implemented bythe phase shifted bridge controller.

The system 11 may be configured for scalable coupling modes such thatthe system 11 can operate in a plurality of discrete coupling modes. Thesystem 11 may include any number of discrete coupling modes and thenumber of discrete coupling modes can depend on the particularimplementation. For example, the system 11 may include two discretecoupling modes, three discrete coupling modes, four discrete couplingmodes, and so on. The number of discrete coupling modes in a particularsystem 11 may correspond to the number of different discreteconfigurations into which the system 11 may be shifted. In a system 11that implements a variable transformer topology, the number of discretecoupling modes may correspond to the number of different possiblecombinations of individual transformer legs 1692 shifted in or out ofthe variable transformer section 1676. In a system 11 that switchesbetween or among different subharmonics of the power transmissionfrequency, the number of discrete coupling modes may correspond to thenumber of different possible subharmonics on which power can betransferred. In a system 11 that implements a phase shifted bridgecontroller, the number of discrete coupling modes may correspond to thenumber of different possible phase shifts that can be implemented by thephase shifted bridge controller.

FIG. 20 is a graph 2000 that illustrates the operation of a system 11that implements two coupling modes by way of example. The graph 2000compares the amount of coupling (shown on the x-axis) to the amount ofreal power dissipated by the secondary (shown on the y-axis). The graph2000 includes a first curve 2004 that shows the delivered power over abroad range of coupling amounts for a first coupling mode. The graph2000 also includes a second curve 2008 that shows the delivered powerover a broad range of coupling amounts for a second coupling mode. Thetwo coupling modes corresponding to the two curves 2004, 2008 may beimplemented using any appropriate mechanism including a variabletransformer topology, subharmonic power transfer, a phase shifted bridgecontroller, and so on. As shown in FIG. 20, as the amount of couplingdecreases to around 0.1 to 0.05, the amount of real power dissipated bythe secondary starts to increase rapidly. This is due to the fact thatpoor coupling leads to greater I²R losses and greater real powerconsumption. This can lead to unwanted heating in the secondary. On agiven curve 2004, 2008, the amount of a coupling can vary as a functionof the separation distance between the coils 1648, 1656. In particular,greater separation distances result in smaller coupling amounts. Thus,as the separation between the coils 1648, 1656 increases, the operatingpoint of the system moves further to left in FIG. 20. Here, theoperating point moves along either the first curve 2004 or the secondcurve 2008 depending on whether the system 11 operates in the first orsecond coupling mode. Using information such as provided in FIG. 20, thesystem 11 can be programmed to implement an extended coupling range.Specifically, in order to increase the coupling range, the system 11 mayoperate along the first curve 2004 for a first range of coil 1648, 256separations and along a second curve 2008 for a second range of coil1648, 256 separations.

Controller Inputs and System Monitoring

The first processor 130 may be configured to shift the system 11 intodifferent scalable power and/or coupling modes based on input such asdata from communication channels, programmed timers, and/or systemmonitoring parameters and calculations. As described in greater detailbelow, the system 11 may include one or more communication channelswhich can be used to transmit data from the secondary back to theprimary. This data may be provided as input to the first processor 130,which may then shift the system 11 into different scalable power and/orcoupling modes based on the data. The system may also includeprogrammable timers that can be used to track the amount of time thathas elapsed since the occurrence of a particular event. Data from thesetimers may be provided as input to the first processor 130, which maythen shift the system 11 into different scalable power and/or couplingmodes based on the timing data. In other embodiments, the system 11 maymeasure and/or calculate various parameters associated with powertransfer from the primary to the secondary. More specifically, thesystem 11 may be configured to derive various parameters based oncurrent and/or voltages measurements made on the primary side. Thesecurrent and/or voltages measurements may be used to calculate orestimate the coupling coefficient between the primary and the secondary,heat flux or temperature in the secondary, and heat flux or temperaturein the primary. Primary side current and/or voltage measurements mayalso be used to determine if an external interference is present betweenthe primary and the secondary. The system 11 may then use thesecalculations, estimations, and determinations to support shifting intodifferent scalable power and/or coupling modes.

Communication Channels

The system 11 may include one or more communication channels which canbe used to transmit data from the secondary back to the primary. Anyappropriate mechanisms for providing data communication between theprimary and the secondary may be used. For example, the system 11 mayinclude radio frequency (RF) transceivers on the primary and secondaryside that are configured to exchange data when the primary is within acertain distance of the implanted secondary. In other embodiments, theimplanted secondary may modulate the power transfer signal itself with adata signal. This data signal may then be received and demodulated onthe primary side.

Data received over a communication channel between the primary and thesecondary may be received at the primary and provided as input to thefirst processor 130. For example, the system 11 may be executing a powerup sequence and the primary may receive data from the secondaryregarding whether or not the secondary is fully powered up. In anotherexample, the system 11 may include more than one secondary and theprimary may receive data regarding whether or not the correct secondaryis receiving power. In other examples, the primary may receive requestsfrom the secondary to increase or decrease the power output or to entera fault mode. Once the controller receives the data transmitted from thesecondary, the first processor 130 may shift the system 11 intodifferent scalable power and/or coupling modes based on the receiveddata.

System Timers

The system may also include programmable timers that can be used totrack the amount of time that has elapsed since the occurrence of aparticular event. For example, the system 11 may track the time that haselapsed since the system began a power up sequence. In other examples,may track the time that has elapsed since a fault condition was detectedor since a change in a coupling condition has detected. Any appropriatemechanisms for tracking the passage of time may be used. For example,the controller may include interrupt driven timers or timers that arepolled by the CPU. Data from these timers may be provided as input tothe first processor 130, which may then shift the system 11 intodifferent scalable power and/or coupling modes based on the timing data.

Coupling Calculations

The system 11 may be configured to calculate the amount of coupling thatexists between the primary and secondary. The first processor 130 maythen shift the system 11 into different scalable power and/or couplingmodes based on the amount of coupling that exists between the primaryand secondary. More specifically, the first processor 130 may shift to ahigher power mode or to a higher coupling if it is determined that thecurrent coupling between the primary and secondary is not optimal. Inaddition to using coupling calculations to support shifting to differentscalable power and/or coupling modes, the system 11 may also usecoupling calculations in the course of determining fault conditions suchas excess temperature or heat flux in the secondary.

Referring to FIGS. 16A-C, the system 11 may be configured to calculatethe amount of coupling that exists between the external coil 1648 andthe internal coil 1656. In Equation (1), the amount of coupling betweenthe coils 1648, 1656 is represented by the coefficient k, which rangesfrom 0.0 to 1.0. Greater values for the coupling coefficient k indicategreater amounts of coupling between the coils 1648, 1656.

The coupling coefficient k is typically a function of the amount ofseparation between the coils 1648, 1656. This aspect of the couplingcoefficient k can be illustrated with reference to FIG. 17A and FIG.17B. In FIG. 17A, the external coil 1648 is placed against the subject'sskin 1664, in close proximity to the implanted internal coil 1656. InFIG. 17B, the external coil 1648 is removed by a certain distance fromthe subject's skin 1660 and thus from the implanted internal coil 1656.This difference in the amount of separation between the coils 1648, 1656in FIG. 17A and the coils 1648, 1656 in FIG. 17B will typically inresult in these two coil placements having a different amount ofcoupling and thus different values for the coefficient k.

Over a certain range of coil separation distances, smaller distancesbetween the coils 1648, 1656 correspond to greater amounts of couplingand thus k values that are closer to 1.0. Similarly, within this samerange of coil separation distances, larger distances between the coils1648, 1656 correspond to lesser amounts of coupling and thus k valuesthat are closer to 0. Assuming that the coil placements shown in FIG.17A and FIG. 17B fall within this range separation distances, the coilplacement of FIG. 17A has a greater amount of coupling and thus a higherk value in comparison to the coil placement of FIG. 17B.

The system 11 may calculate the amount of coupling that exists betweenthe external coil 1648 and the internal coil 1656 based on regulationtiming parameters associated with the operation of the power circuit1532. Regulation timing parameters used in coupling calculations includethe power mode duty cycle DC_(on) and the duration of the idle modeperiod T_(off). DC_(on) is the duration of the power mode T_(on) overthe duration of the regulation period T_(reg), where the regulationperiod T_(reg) equals the power mode period T_(on) plus idle mode periodT_(off). As described in detail in connection with FIG. 19, one or moreof these regulation timing parameters may be observable throughmeasurements made on the primary side of the system 11. For a circuithaving the series-series topology shown in FIG. 15, embodimentsdiscussed herein make use of the following equation when estimating theamount of coupling between the external coil 1648 and the internal coil1656:

k=α·Toff·DC _(on) +β·DCon−γ  (2)

For each unique design of coils there are a set of values for α, β, andγ that satisfy Equation (2), where κ is the coupling coefficient betweenthe external coil 1648 and the internal coil 1656. In operation, thesystem 11 can use Equation (2) to estimate the amount of coupling thatexists between the external coil 1648 and the internal coil 1656 at anygiven time. Here, the system 11 can be programmed with values for α, β,and γ that correspond to the particular coil design being used. Theregulation timing parameters DC_(on) and T_(off) can be derived fromcurrent or voltage measurement made on the primary side as power istransferred between the external assembly 1504 and the internal assembly1508. In some implementations, the system 11 derives the regulationtiming parameters from a current signal such as generated by the currentsensor 1620, which measures the current present in the external coil1648. The system 11 can also derive the regulation timing parametersfrom voltage signals generated by voltage sensors disposed a variouslocations on the primary side. For example, system 11 may derive theregulation timing parameters from voltage signals generated by voltagesensors arranged across either the coil 1648 or the capacitor 1652 ofthe external network 15.

Referring to FIG. 21, aspects of system 11 that relate to derivingregulation timing parameters from primary side measurements aredescribed in greater detail. FIG. 21 is an illustration of variouswaveform traces that represent signals that are present in the system 11as power is transferred between the external assembly 1504 and theinternal assembly 1508. FIG. 21 illustrates the magnitude of the voltageacross the power supply capacitor associated with the regulator circuit1544 as this signal changes over time. This voltage is labeled asV_(OUT) and is referred to with reference number 2104. As can be seen inFIG. 21, V_(OUT) gradually decreases as current is drawn from thecapacitor associated with the regulator circuit 1544, and graduallyincreases when current is supplied to the capacitor from the rectifier1652. The gradual decrease of V_(OUT) corresponds to the power circuit1532 being in the idle mode. Similarly, the gradual increase of V_(OUT)corresponds to the power circuit 1532 being in the power supply mode.

FIG. 21 additionally illustrates a current signal that representscurrent present in the external coil 1648 as power is transferredbetween the external assembly 1504 and the internal assembly 1508. Thiscurrent signal is labeled as I₁ and is referred to with reference number2108. The current signal I₁ can be generated by the current sensor 1620and is an example of a primary side signal that the system 11 may use toderive regulation timing parameters. FIG. 21 also illustrates a currentsignal that represents current present in the internal coil 1656 aspower is transferred between the external assembly 1504 and the internalassembly 1508. This current signal is labeled as I₂ and is referred towith reference number 2112. As can be seen in FIG. 21, the amplitudes ofboth I₁ and I₂ are smaller when the power circuit 1532 is in the idlemode as compared to when the power circuit 1532 is in the power supplymode. I₁ is lower because V₂ drops to approximately zero in response tothe shorting switches 1672 closing so as to short the internal resonantnetwork 17. I₂ is lower because V₁ drops to a fraction of its power modevalue in response to the power bridge 148 operating at a sub-harmonicfrequency.

T_(off) is defined as the duration of the short period and thuscorresponds to the length of time that the shorting switches 1672 areclosed so as to short the internal coil network 17. Stated another way,T_(off) corresponds to the length of time that the power circuit 1532 isin the idle mode. T_(off) can be derived from measurements of thecurrent that is present in the external coil 1648 as power istransferred between the external assembly 1504 and the internal assembly1508. Specifically, as can be seen in FIG. 21, T_(off) can be measuredby calculating the time that elapses between when I₁ transitions to alow amplitude and when I₁ transitions back to the high amplitude.Alternatively, T_(off) can be calculated by subtracting the power modeperiod T_(on) from the regulation period T_(reg). An example time framefor a T_(off) measurement is given in FIG. 21 and is generallyidentified with reference number 2116.

T_(on) is defined as the duration of the un-shorted period and thuscorresponds to length of time that the shorting switches 1672 are openso as to allow current to flow from the internal resonant network 17,through the rectifier 1652, and out to the conductor line 1640/1644.Stated another way, T_(on) corresponds to the length of time that thepower circuit 1532 is in the power supply mode. T_(on) can be derivedfrom measurements of the current that is present in the external coil1648 as power is transferred between the external assembly 1504 and theinternal assembly 1508. Specifically, as can be seen in FIG. 21, T_(on)can be measured by calculating the time that elapses between when htransitions to a high amplitude and when I₁ transitions back to the lowamplitude. Alternatively, T_(on) can be calculated by subtracting theidle mode period T_(off) from the regulation period T_(reg). An exampletime frame for a T_(on) measurement is given in FIG. 21 and is generallyidentified with reference number 2120.

T_(reg) is defined as the duration of the regulation period and thuscorresponds to the length of time that the shorting switches are 1672are open, plus the length of time that the shorting switches 1672 areclosed. Stated another way, T_(reg) corresponds to the length of timethat the power circuit 1532 is in idle mode, plus the length of timethat the power circuit is in power supply mode. T_(reg) can be derivedfrom measurements of the current that is present in the in the externalcoil 1648 as power is transferred between the external assembly 1504 andthe internal assembly 1508. As can be seen in FIG. 21, T_(reg) can bemeasured by calculating the time that elapses between when I₁transitions to a high amplitude a first time and when I₁ transitionsback to a high amplitude a second subsequent time. Alternatively,T_(reg) can be calculated by adding the power mode period T_(on) and theidle mode period T_(off) together. An example time frame for a T_(reg)measurement is given in FIG. 21 and is generally identified withreference number 2124.

DC_(on) is the power mode duty cycle. DC_(on) is defined as the durationof the power mode T_(on) over the duration of the regulation periodT_(reg). Typically, current or voltage measurements are not taken thatyield DC_(on) directly. Rather, DC_(on) is derived from otherparameters, which themselves are derived from current measurements.Specifically, DC_(on) can be derived by dividing the power mode periodT_(on) by the regulation period T_(reg).

Because there are a set of values for α, β, and γ that satisfy Equation(2) for each unique design of coils, Equation (2) can be used toestimate the coupling coefficient k as power as is transferred betweenthe external assembly 1504 and the internal assembly 1508. Specifically,in a particular implementation, the system 11 can be programmed with thevalues for α, β, and γ that correspond to the coil design used in thatparticular implementation. As the system transfers power between theexternal assembly 1504 and the internal assembly 1508, the power modeduty cycle DC_(on) and the idle mode period T_(off) can be derived fromprimary side measurements. As illustrated in FIG. 21, DC_(on) andT_(off) can be derived from the current signal I₁, which is generatedthe current sensor 1620 and which represents current present in theexternal coil 1648. In other examples, the system 11 can derive theregulation timing parameters from voltage signals generated by voltagesensors disposed a various locations on the primary side, such as acrosseither the coil 1648 capacitor 1652 of the external network 15. OnceDC_(on) and T_(off) are derived, Equation (2) can be used to calculate avalue for the coupling coefficient k.

The approach to calculating the coupling coefficient k that is embodiedin Equation (2) was verified on collected data from functional TETSsystems 1500. Equation (2) was applied to collected short and duty cycledata. Several of these data samples are plotted in FIG. 22. It should beappreciated that Equation (2) applies to the series-series topologyillustrated in FIG. 15. In accordance with alternative embodiments,other equations akin to Equation (2) can be derived for alternativetopologies such as series-parallel, parallel-series, parallel-paralleland so on.

The system 11 may use coupling coefficient calculations to supportshifting the system 11 into different scalable power and/or couplingmodes based on the amount of coupling that exists between the primaryand secondary. More specifically, the first processor 130 may shift todifferent power or current coupling modes if coupling is not optimal.Alternatively or in combination, the first processor 130 may usecoupling calculations as part of determining fault conditions. Thesecontroller operations are described in greater detail below inconnection with FIG. 24 through FIG. 32.

Heat Flux and Temperature Calculations

The system 11 may additionally be configured to estimate the amount ofthe heat flux and/or temperature levels as power is transferred from theexternal assembly 1504 to the internal assembly 1508. Higher levels ofheat flux or temperature in the system 11 can lead to tissue damage orotherwise injure the subject with whom the system 11 is used. Excessiveheat flux or temperature can occur in either the primary or thesecondary. Thus, in order to ensure safety of the subject, the system 11may monitor heat flux and/or temperature levels in the either or both ofthe primary or the secondary. If the amount of temperature or heat fluxin either the primary or the secondary indicates a fault condition, thefirst processor 130 may then shift the system 11 into different scalablepower and/or coupling modes in order to mitigate the fault condition.

The system 11 may monitor heat flux and/or temperature by monitoring theamount of current that is flowing in various parts of the system 11.Higher current levels generate I²R losses, which generate heat. In onerespect, excessive heat flux can be generated when coupling between theprimary and the secondary is non-optimal. Here, non-optimal coupling canlead to high currents, which generate due excess heat due to parasiticresistances that may be present in the inductors 1648, 1656 or othercomponents of the internal or external networks 15, 17. When highercurrent levels are present in the system 11, heat flux tends to increaseand temperatures tend to rise in a predictable manner. Higher currentlevels can be present in either or both of the primary or the secondary.Thus, the system 11 may monitor heat flux and/or temperature bymonitoring currents present in either the primary and/or secondary. Inone embodiment, current levels in the system are monitored throughvarious measurements taken on the primary side of the system 11.

For current levels in the primary, the system 11 may make directmeasurements using meters or probes that are attached to components inthe external resonant network 15. In one example, the system 11 maymeasure the primary side current using the current sensor 1620, whichmeasures the current present in the external coil 1648. The system 11may also calculate the primary side current from based on voltagesignals generated by voltage sensors disposed a various locations on theprimary side, such as across either the coil 1648 or the capacitor 1652of the external network 15. For example, the system 11 may calculate theprimary side current using a known inductance value for the coil 1648and a measured value for the voltage across the coil 1648.Alternatively, the system 11 may calculate the primary side currentusing a known capacitance value for the capacitor 1652 and a measuredvalue for the voltage across the capacitor 1652.

For current levels in the secondary, the system 11 may measure certainregulation timing parameters on the primary side and estimate secondarycurrent levels based on these primary side measurements. Morespecifically, the system 11 may first estimate the amount of couplingbetween the primary and the secondary based on regulation timingparameter measurements. The system 11 may then use the estimatedcoupling measurements made on the primary to estimate current levels inthe secondary. Thus, in one respect, the system 11 may calculate theamount of coupling that exists between the external coil 1648 and theinternal coil 1656 as part of estimating heat flux or temperature levelsin the internal assembly 1508. Lower amounts of coupling generate heatbecause poor coupling results in higher currents being generated in thecoils 1648, 1656. For a circuit having the series-series topology shownin FIG. 15, the inverse relationship between coupling and current in thesecondary can be appreciated by rewriting Equation (1) in terms of I₂:

$\begin{matrix}{I_{2} = \frac{V_{p}}{k*w*L_{eq}}} & (3)\end{matrix}$

The coupling coefficient k appears in the denominator of Equation (3).Thus, decreases in the value of the coupling coefficient k correspond toincreases in the value of the current in secondary.

As can be seen from Equation (3), the coupling coefficient k is oneparameter needed to calculate the current I₂ that is present in thesecondary. Another parameter needed for this calculation is V₁ (V_(p) inEquation (3)), the voltage across the external resonant network 15. V₁is proportional to power supply DC voltage V. Typically, the powersupply voltage V_(in) does not change. Thus, with the exception that V₁scales with frequency when the system shifts to a different subharmonic,V₁ is static. Thus, V₁ can be derived from system settings and istypically known without any measurements. For full-bridge inverter, therelationship between V_(in) and V₁ is governed by the followingequations:

V ₁=4·V _(in)/π  (4)

Once values for k and V₁, are determined, Equation (3) can be used tocalculate the current I₂ that is present in the secondary. As describedabove, the current I₁ that is present in the primary can be determinedthrough direct measurements using meters or probes associated with theprimary. Once values for I₁ and I₂ are determined, heat flux in theprimary and/or the secondary can be determined. Heat flux in the primaryis based on the current I₁ in the primary coil, the known parasiticresistance of primary coil, and the surface area of primary coil. Heatflux in the secondary is based on the current I₂ in the secondary coil,the known parasitic resistance of secondary coil, and the surface areaof the secondary coil. The heat flux in either the primary or thesecondary can be determined with the following equation:

Heat Flux=(I _(rms) ² *R)/Coil Surface Area.  (5)

The temperature of the coils 1648, 1656 can be estimated based on theamount of heat flux that is determined to be present in either theprimary or the secondary. Generally, the correlation between temperatureand heat flux depends on the environment in which either the primary orthe secondary operates. Thus, the system 11 may be programmed with anequation, a look-up table, or other data structure that correlates heatflux amounts to temperature changes in the primary and/or the secondary.The system 11 may be programmed with different equations, look-uptables, or other data structures for the primary and the secondarybecause these system components each are located in differentenvironments.

The primary is located outside of the subject and thus the temperatureof the primary can be estimated based on heat flux calculations and thepredictable behavior of the primary as it operates in the open air. Inone respect, temperature changes can be estimated based on heat fluxlevel estimations made over a certain time interval. Temperatureincreases can be correlated with sustained elevated heat flux levels.Similarly, temperature decreases can be correlated with lower heat fluxlevels that are maintained over time. The system 11 may be programmedwith an equation, a look-up table, or other data structure thatquantifies these correlations and that may be accessed whendeterminations of the temperature in primary are made.

Depending on the location of the coil 1648 in the body there may be aspecific relation between coil temperature and heat flux emanating fromthe coil 1648. For various current levels, animal studies can be used toestimate secondary heat flux amounts and safety levels. Results from onesuch animal study is shown in FIG. 23. Previous studies by PennsylvaniaState University have found that 15 mW/cm² level is safe. The system 11can be programmed based on the heat flux assessment shown in FIG. 23 orwith other appropriate heat flux assessments. As was the case for theprimary, temperature increases in the secondary can be correlated withsustained elevated heat flux levels; and temperature decreases can becorrelated with lower heat flux levels that are maintained over time.The system 11 may be programmed with an equation, a look-up table, orother data structure that quantifies these correlations and heatassessments and that may be accessed when determinations of thetemperature in secondary are made. The heat flux assessment of FIG. 23is shown by way of example and limitation. It should be appreciated thatthe heat flux assessment shown in FIG. 23 can be adjusted based onfuture animal studies and that the heat flux to temperature correlationsused by the system 11 can be based on animal studies which can beupdated on an on-going basis.

Interference Calculations

The system 11 may additionally take measurements on the primary side soas to determine if any interference exists between the coils 1648, 1656.Interference can occur due to the presence of metal or a metallic objectnear one or both of the coils 1648, 1656. The presence of a metal or ametallic object can de-tune the coils 1648, 1656 by altering the amountand character of mutual inductance that exits between the coils 1648,1656. The de-tuning can appear on the primary side as a phase shiftbetween the voltage V₁ across the external resonant network 15 and thecurrent h through the external resonant network 15. Thus, the system 11can determine if any interference exists between the coils 1648, 1656 bymeasuring this phase difference. Specifically, the system measures thevoltage V₁ across the external resonant network 15 and the current I₁through the external resonant network 15 over a predetermined timeperiod using the techniques described above. These measurements are thencompared to determine if any phase shift exists. If the system 11detects a phase shift, the system 11 may determine that the coils 1648,1656 have become detuned due to the presence of an interfering metal ormetallic object.

The system 11 may take one or more corrective actions in response todetermining that the coils 1648, 1656 have become detuned. In somecases, the system 11 may provide an alert that indicates to the userthat an interfering metal or metallic object is present. The system 11may then reject estimations made of the current I₂ in the secondaryuntil the user removes the metal or metallic object. The system 11 mayreject estimations made of the current I₂ because Equation (2) is basedon the assumption that the voltage V₁ and the current are in phase.Specifically, Equation (2) is based on the assumption that resonantcircuit operates at resonance and that there is specific relationshipbetween the resonant circuit parameters, namely L1, C1, k, M, L2, C2.This relationship breaks down when metal is introduced. This, if thevoltage V₁ and the current I₁ are out of phase, Equation (2) may ceaseto accurately characterize the behavior of the system 11. In othercases, the system 11 may compensate for the phase difference between thevoltage V₁ and the current I₁ rather than wait for the user to removethe interfering metal or metallic object. Specifically, the system 11may alter the manner in which the power bridge 148 operates. In oneembodiment, the power management module 140 can change control frequencyof the power bridge 148 to compensate for a shift in resonance thatoccurs due to the fact that metal objects change mutual and leakageinductance of the coil and as result change resonance point of thesystem.

Load Determinations

The system 11 may be configured to determine the amount of electricalloading that is present at the secondary. For example, the system 11 maymonitor the duty cycle of the power transfer signal on the primary sideto determine the loading conditions that are present in the secondary.In another example, the system 11 may receive data regarding the loadingconditions through a communication sent from the secondary to theprimary. Based on the loading conditions, the first processor 130 mayshift the system 11 into different scalable power and/or coupling modes,if appropriate. More specifically, the first processor 130 may shift toa higher power mode or to a higher coupling if it is determined that theloading conditions indicate a reduced need for power.

Controller Operations

Turning now to operations of the first processor 130 that function toset the power mode and/or the coupling mode of the system 11, referenceis made to FIGS. 24-37. As illustrated in FIGS. 24-37, the firstprocessor 130 may set the power mode and/or the coupling mode in whichthe system 11 operates based on input such as data received fromcommunication channels, programmed timers, and/or system monitoringparameters and calculations. The methods and operations illustrated inFIG. 24-37 may be applied in connection with any appropriate mechanismfor implementing a scalable power and/or coupling modes including avariable transformer topology, subharmonic power transfer, a phaseshifted bridge controller, and so on.

Turning first to operations of the first processor 130 that function toset the power mode in which the system 11 operates, reference is made toFIG. 24. FIG. 24 is a flow chart 1000 that illustrates a method ofshifting between or among scalable power modes in accordance withembodiments discussed herein. The method illustrated by the flow chart1000 includes operations executed by the first processor 130 shown inFIG. 1. The first processor 130 is external to the subject and so may beconfigured to receive input signals from various points on the primaryside of the system 11. As set forth in flow chart 1000, the firstprocessor 130 may shift between or among scalable power modes based oninputs received on the primary side of the system 11.

Initially, in operation 2404, the first processor 130 sets an initialpower mode. The specific signals output by the first processor 130 toset the power mode may depend on the mechanism implemented by the system11 for shifting between power modes. In a system 11 that implements avariable transformer topology, the first processor 130 may providecontrol inputs that set a specific combination of individual transformerlegs 1692 shifted in or out of the variable transformer section 1676. Ina system 11 that switches between or among different subharmonics of thepower transmission frequency, the first processor 130 may providecontrol inputs that set the inverter 148 to a specific subharmonicfrequency. In a system 11 that implements a phase shifted bridgecontroller, the first processor 130 may provide control inputs that setthe voltage and current signals of the inverter 148 to a specific phasedifference.

In operation 2408, the system operates in the currently set powertransfer mode. Specifically, power is output from external assembly1504, transferred across the skin 1664 of the subject, and is receivedby the internal assembly 108. Power received by the internal assemblycharges a power supply capacitor or other component associated with theregulator circuit 1556, as needed. Based on the charging needs of thepower supply capacitor, a regulator 156 component of the internalassembly 108 may shift between a power supply mode and an idle mode. Theexternal assembly 1504 may respond to these shifts made by the regulatorby changing an amount of power supplied from the external assembly 1504.

In operation 2412, the first processor 130 determines if the system 11should be shifted to a different power mode. The first processor 130makes this determination based on input such as data received fromcommunication channels, programmed timers, and/or system monitoringparameters and calculations. Specific first processor 130 operationsthat carry out these determinations are described in greater detail inFIGS. 25-29. If, in operation 2412, the first processor 130 determinesthat the system 11 need not be shifted to a different power mode,operation 2408 may again be executed following operation 2412. If, inoperation 2412, the first processor 130 determines that the system 11does need to be shifted to a different power mode, operation 2416 may beexecuted following operation 2412.

In operation 2416, the system shifts into a different power mode. Thespecific signals output by the first processor 130 to shift the powermode may depend on the mechanism implemented by the system 11 forshifting between power modes. As mentioned, the first processor 130 mayprovide control inputs that set a specific combination of individualtransformer legs 1692 shifted in or out of the variable transformersection 1676, provide control inputs that set the inverter 148 to aspecific subharmonic frequency, provide control inputs that set thevoltage and current signals of the inverter 148 to a specific phasedifference, and so on. Once a new power mode has been set, operation2408 may again be executed following operation 1016.

FIG. 25 is a flow chart 2500 that illustrates first processor 130operations that provide for determining whether or not the system shouldshift based on input received from communication channels. Flow chart2500 illustrates a specific implementation of operation 2412 shown inFIG. 24. Initially, in operation 2504, the first processor 130 monitorscommunication channels between the primary and the secondary. Asmentioned, the system 11 may include one or more communication channelswhich can be used to transmit data from the secondary back to theprimary. In operation 2504, the first processor 130 may monitor thecommunication channels including receiving as input data transmittedfrom the secondary to the primary. In operation 2508, the firstprocessor 130 determines if any communications are related to powershifting. Examples of data related to power shifting includes dataindicating the end of a power up sequence, data indicating if thecorrect secondary is being powered, data regarding specific requests toincrease or decrease power output, and data providing requests to entera fault mode. In operation 2512, the first processor 130 determines thesystem should be shifted into a different power mode. For example, thefirst processor 130 may shift to a lower power mode after an initialpower up, if the incorrect secondary is being powered, if lower power isspecifically requested, or if a fault mode is requested. By way offurther example, the first processor 130 may shift to a high power modein response to a specific request for more power or if a fault mode isrequested.

FIG. 26 is a flow chart 2600 that illustrates first processor 130operations that provide for determining whether or not the system 11should shift based on system timers. Flow chart 2600 illustrates aspecific implementation of operation 2412 shown in FIG. 24. Initially,in operation 2604, the first processor 130 monitors system timers. Asmentioned, the system 11 may also include programmable timers that canbe used to track the amount of time that has elapsed since theoccurrence of a particular event, such as the amount of time that haselapsed since the system began a power up sequence, or the time that haselapsed since a fault condition was detected or since a change in acoupling condition was detected. In operation 2604, the first processor130 may monitor the programmable timers including receiving as inputtiming data that is provided as output from the timers. In operation2608, the system determines if any system timers have expired. Inoperation 2612, the system determines if the system should be shiftedinto a different power mode. For example, the first processor 130 mayshift to a lower power mode if an expired timer indicates that apredetermined time has elapsed since an initial power up, or if anexpired timer indicates that a predetermined time has elapsed since afault condition was detected.

FIG. 27 is a flow chart 2700 that illustrates first processor 130operations that provide for determining whether or not the system 11should shift based on calculated coupling amounts. Flow chart 2700illustrates a specific implementation of operation 2412 shown in FIG.24. Initially, in operation 2704, the first processor 130 monitorsregulation timing parameters on the primary side of the system 11. Asmentioned, the first processor 130 may monitor regulation timingparameters of the secondary through voltage and/or current measurementstaken on the primary side of the system 11. In operation 2708, thesystem determines if the regulation timing parameters indicate changedcoupling conditions. As described in greater detail in connection withFIG. 33, the first processor 130 may be configured to calculate theamount of coupling between the primary and the secondary based on dutycycle calculations and idle mode duration measurements. In operation2712, the system determines if the system should be shifted into adifferent power mode. For example, the first processor 130 may shift toa lower power mode if the coupling between the primary and secondary isnon-optimal. By way of further example, the first processor 130 mayshift to a higher power mode if the coupling between the primary and thesecondary is strong.

FIG. 28 is a flow chart 2800 that illustrates first processor 130operations that provide for determining whether or not the system 11should shift based on whether or not a fault condition is detected. Flowchart 2800 illustrates a specific implementation of operation 2412 shownin FIG. 24. Initially, in operation 2804, the first processor 130monitors system status parameters on the primary side of the system 11.As described in greater detail in connection with FIG. 33-37, the firstprocessor 130 may be configured to monitor system status parameters suchas coupling, heat flux, and temperature. In operation 2808, the systemdetermines if any system status parameters indicate a fault condition.Here, the first processor 130 may determine if the coupling issufficiently below optimal levels so as to adversely affect the system11. The first processor 130 may also determine if the temperature and/orheat flux levels exceed established safety limits. In operation 2812,the system determines if the system should be shifted into a differentpower mode. For example, the first processor 130 may shift to a lowerpower mode if the coupling between the primary if the coupling issufficiently below optimal levels so as to adversely affect the system11 or if the temperature and/or heat flux levels exceed establishedsafety limits.

FIG. 29 is a flow chart 2900 that illustrates first processor 130operations that provide for determining whether or not the system 11should shift based on loading conditions that are present in thesecondary. Flow chart 2900 illustrates a specific implementation ofoperation 2412 shown in FIG. 24. Initially, in operation 2904, the firstprocessor 130 monitors loading conditions in the secondary based onsignals measured in the primary. As mentioned, the system 11 may beconfigured to determine the amount of electrical loading that is presentat the secondary by monitoring the duty cycle of the power transfersignal on the primary side, by receiving data regarding the loadingconditions through a communication sent from the secondary to theprimary, or by other appropriate procedures. In operation 2908, thesystem determines if loading conditions have changed. In operation 2912,the system determines if the system should be shifted into a differentpower mode based on any changed loading conditions. For example, thefirst processor 130 may shift to a lower power mode if it is determinedthat the loading conditions indicate a reduced need for power.

Turning now to operations of the first processor 130 that function toset the coupling mode in which the system 11 operates, reference is madeto FIG. 30. FIG. 30 is a flow chart 3000 that illustrates a method ofshifting between or among scalable coupling modes in accordance withembodiments discussed herein. The method illustrated by the flow chart3000 includes operations executed by the first processor 130 shown inFIG. 1. The first processor 130 is external to the subject and so may beconfigured to receive input signals from various points on the primaryside of the system 11. As set forth in flow chart 3000, the firstprocessor 130 may shift between or among scalable coupling modes basedon inputs received on the primary side of the system 11.

Initially, in operation 3004, the first processor 130 sets an initialcoupling mode. The specific signals output by the first processor 130 toset the coupling mode may depend on the mechanism implemented by thesystem 11 for shifting between coupling modes. In a system 11 thatimplements a variable transformer topology, the first processor 130 mayprovide control inputs that set a specific combination of individualtransformer legs 1692 shifted in or out of the variable transformersection 1676. In a system 11 that switches between or among differentsubharmonics of the power transmission frequency, the first processor130 may provide control inputs that set the inverter 148 to a specificsubharmonic frequency. In a system 11 that implements a phase shiftedbridge controller, the first processor 130 may provide control inputsthat set the voltage and current signals of the inverter 148 to aspecific phase difference.

In operation 3008, the system operates in the currently set couplingmode. Specifically, power is output from external assembly 1504,transferred across the skin 1664 of the subject, and is received by theinternal assembly 108. Power received by the internal assembly charges apower supply capacitor or other component associated with the regulatorcircuit 1556, as needed. Based on the charging needs of the power supplycapacitor, a regulator 156 component of the internal assembly 108 mayshift between a power supply mode and an idle mode. The externalassembly 1504 may respond to these shifts made by the regulator 156 bychanging an amount of power supplied from the external assembly 1504.

In operation 3012, the first processor 130 determines if the system 11should be shifted to a different coupling mode. The first processor 130makes this determination based on input such as data received fromcommunication channels, programmed timers, and/or system monitoringparameters and calculations. Specific first processor 130 operationsthat carry out these determinations are described in greater detail inFIGS. 31-32. If, in operation 3012, the first processor 130 determinesthat the system 11 need not be shifted to a different coupling mode,operation 3008 may again be executed following operation 3012. If, inoperation 3012, the first processor 130 determines that the system 11does need to be shifted to a different coupling mode, operation 3016 maybe executed following operation 3012.

In operation 3016, the system shifts into a different coupling mode. Thespecific signals output by the first processor 130 to shift the couplingmode may depend on the mechanism implemented by the system 11 forshifting between coupling modes. As mentioned, the first processor 130may provide control inputs that set a specific combination of individualtransformer legs 1692 shifted in or out of the variable transformersection 1676, provide control inputs that set the inverter 148 to aspecific subharmonic frequency, provide control inputs that set thevoltage and current signals of the inverter 148 to a specific phasedifference, and so on. Once a new coupling mode has been set, operation3008 may again be executed following operation 3016.

FIG. 31 is a flow chart 3100 that illustrates first processor 130operations that provide for determining whether or not the system 11should shift based on calculated coupling amounts. Flow chart 3100illustrates a specific implementation of operation 3012 shown in FIG.30. Initially, in operation 3104, the first processor 130 monitorsregulation timing parameters on the primary side of the system 11. Asmentioned, the first processor 130 may monitor regulation timingparameters through voltage and/or current measurements taken on theprimary side of the system 11. In operation 3108, the system determinesif the regulation timing parameters indicate changed couplingconditions. As described in greater detail in connection with FIG. 33,the first processor 130 may be configured to calculate the amount ofcoupling between the primary and the secondary based on duty cycle andidle mode durations calculations. In operation 3112, the systemdetermines if the system should be shifted into a different couplingmode. For example, the first processor 130 may shift to a lower couplingmode if the coupling between the primary and secondary is non-optimal.By way of further example, the first processor 130 may shift to a highercoupling mode if the coupling between the primary and the secondary isstrong.

FIG. 32 is a flow chart 3200 that illustrates first processor 130operations that provide for determining whether or not the system 11should shift coupling mode based on the placement of the primary coil inrelation to the secondary coil. Flow chart 3200 illustrates a specificimplementation of operation 3012 shown in FIG. 30. Initially, inoperation 3204, the first processor 130 monitors the placement of theprimary coil in relation to the location of the secondary coil. Here,the first processor 130 may approximate the placement of the primarycoil based on coupling calculations as set forth in the FIG. 33.Alternatively, the first processor 130 may utilize proximity sensors orother appropriate mechanisms to determine the placement of the primarycoil in relation to the secondary coil. In operation 3208, the systemdetermines if the coil placement indicates changed coupling conditions.In operation 3212, the system determines if the system should be shiftedinto a different coupling mode based on any changed coupling conditions.For example, the first processor 130 may shift to a lower coupling modeif the placement of the primary coil relative to the secondary coilprovides a non-optimal coupling. By way of further example, the firstprocessor 130 may shift to a higher coupling mode if the placement ofthe primary coil relative to the secondary coil could support a highcoupling amount.

In accordance with present embodiments, first processor 130 may functionto measure and calculate various parameters associated with powertransfer in the TETS system 11. First processor 130 may then use theseparameters to shift between or among power and/or coupling modes. Forexample, first processor 130 may shift between or among power and/orcoupling modes responsive to potential decoupling between the coils1648, 1656, estimated elevated heat flux levels in the primary orsecondary, and/or estimated elevated temperature levels in the primaryor secondary. These aspects of the present disclosure are described inconnection with the methods and operations illustrated in FIGS. 33-37.

Turning first to first processor 130 operations that function tocalculate a coupling coefficient k, reference is made to FIG. 33. FIG.33 is a flow chart 3300 that illustrates a method of calculating acoupling coefficient k in accordance with embodiments discussed herein.The method illustrated by the flow chart 3300 includes operationsexecuted by first processor 130 shown in FIG. 1. First processor 130 isexternal to the subject and so may be configured to receive inputsignals from various points on the primary side of the system 11. As setforth in flow chart 3300, the power management module 140 may calculatethe coupling coefficient k between the external coil 1648 and theinternal coil 1656 by performing various calculations based on theprimary side input signals.

Initially, in operation 3300, the system 11 determines the duration ofthe regulation period T_(reg). The regulation period T_(reg) correspondsto the duration of the power supply period T_(on), plus the duration ofthe idle period T_(off). An example regulation period T_(reg) 2124 isillustrated in connection with the example waveform traces shown in FIG.21. The system 11 may determine the duration of the regulation periodT_(reg) based on measurements of the current in the external resonantnetwork 15 that are made as power is transferred from the externalassembly 1504 to the internal assembly 1508. Specifically, the currentsensor 1620 may generate an output signal corresponding to the magnitudeof the current flowing through the external coil 1648, which signal ispassed as input to the first processor 130. First processor 130 may thenmonitor the current signal to determine when the power circuit 1532transitions between the power mode and the idle mode by determining whenthe current signal transitions between a low amplitude and highamplitude. First processor 130 may register a regulation period T_(reg)as occurring between the time when the current signal transitions to ahigh amplitude a first time and the time when the current signaltransitions back to a high amplitude a second subsequent time.

In operation 3308, the system 11 determines the duration of the powermode. An example power mode period T_(on) 2120 is illustrated inconnection with the example waveform traces shown in FIG. 21. The system11 may determine the duration of the power mode period T_(on) based onmeasurements of the current in the external resonant network 15 that aremade as power is transferred from the external assembly 1504 to theinternal assembly 1508. Specifically, the current sensor 1620 maygenerate an output signal corresponding to the magnitude of the currentflowing through the external coil 1648, which signal is passed as inputto the power management module 140. first processor 130 may then monitorthe current signal to determine when the power circuit 1532 transitionsbetween the power mode and the idle mode by determining when the currentsignal transitions between a low amplitude and high amplitude. Firstprocessor 130 may register a power mode period T_(on) as occurringbetween the time when the current signal transitions to a high amplitudeand the time when the current signal transitions to a low amplitude.

In operation 3312, the system 11 calculates the power mode duty cycleDC_(on). DC_(on) is defined as the duration of the power mode T_(on)over the duration of the regulation period T_(reg). First processor 130may determine the power mode duty cycle DC_(on) by dividing the powermode period T_(on) obtained in operation 3308 by the regulation periodT_(reg) obtained in operation 3304.

In operation 3316, the system 11 determines the duration of the idlemode. An example idle mode period T_(off) 2116 is illustrated inconnection with the example waveform traces shown in FIG. 21. The system11 may determine the duration of the idle mode period T_(off) based onmeasurements of the current in the external resonant network 15 that aremade as power is transferred from the external assembly 1504 to theinternal assembly 1508. Specifically, the current sensor 1620 maygenerate an output signal corresponding to the magnitude of the currentflowing through the external coil 1648, which signal is passed as inputto the first processor 130. First processor 130 may then monitor thecurrent signal to determine when the power circuit 1532 transitionsbetween the power mode and the idle mode by determining when the currentsignal transitions between a low amplitude and high amplitude. Firstprocessor 130 may register an idle mode period T_(off) as occurringbetween the time when the current signal transitions to a low amplitudeand the time when the current signal transitions to a high amplitude.

In operation 3320, the system 11 calculates the coupling coefficient kbetween the external coil 1648 and the internal coil 1656. The system 11may determine the coupling coefficient k using Equation (2). Here, thefirst processor 130 may be programmed with values for α, β, and γ thatcorrespond to the particular coil design being used. In calculating thecoupling coefficient k, the first processor 130 may these pre-programmedvalues, as well as the value for the power mode duty cycle DC_(on)obtained in operation 3312 and the value for the idle mode periodT_(off) obtained in operation 3316. Specifically, the first processor130 may enter these programmed and measured values into Equation (2) andin so doing obtain an estimation for the coupling coefficient k betweenthe external coil 1648 and the internal coil 1656.

FIG. 34 is a flow chart 3400 that illustrates a method of estimating asecondary coil heat flux in accordance with embodiments discussedherein. The method illustrated by the flow chart 3400 includesoperations executed by the power management module 140 shown in FIG. 5.The first processor 130 is external to the subject and so may beconfigured to receive input signals from various points on the primaryside of the system 11. As set forth in flow chart 3400, the firstprocessor 130 may calculate the secondary coil heat flux by performingvarious calculations based on the primary side input signals.

Initially, in operation 3404, the system 11 determines the voltage V₁across the external resonant network 15. As mentioned, V₁ isproportional to the power supply DC voltage V_(in), and thus does nottypically change except for scaling with frequency when the systemshifts to a different subharmonic. Thus, V₁ can be derived from systemsettings and is typically known without any measurements. Inimplementations that use a full-bridge inverter, first processor 130 cancalculate V₁ using V_(in) and Equation (4).

In operation 3408, the system 11 calculates the coupling coefficient kbetween the external coil 1648 and the internal coil 1656. As set forthin connection with FIG. 33, the system 11 may use Equation (2) tocalculate the coupling coefficient k based on programmed values for α,β, and γ, and measured values for the power mode duty cycle DC_(on) andthe idle mode period T_(off).

In operation 3412, the system 11 estimates the current I₂ present in theinternal coil 1656 using the voltage V₁ across the external resonantnetwork 15 and the coupling coefficient k between the external coil 1648and the internal coil 1656. The system 11 may determine the current I₂present in the internal coil 1656 using the value for the voltage V₁obtained in operation 3404 and the value for the coupling coefficient kobtained in operation 3408. Specifically, the first processor 130 mayenter these measured values into Equation (3) and in so doing obtain anestimation for the current I₂.

In operation 3416, the system 11 estimates secondary coil heat fluxusing current I₂. As mentioned, heat flux in the secondary is based onthe current I₂ in the secondary coil, the known parasitic resistance ofsecondary coil, and the surface area of the secondary coil. Thus, theheat flux in the secondary can be calculated or otherwise estimatedusing the current I₂ present in the internal coil 1656 as determined inoperation 3412. Here, the power management module 140 can calculate theheat flux in the secondary using Equation (5).

FIG. 35 is a flow chart 3500 that illustrates a method of estimating asecondary coil temperature in accordance with embodiments discussedherein. The method illustrated by the flow chart 3500 includesoperations executed by the first processor 130 shown in FIG. 5. Thefirst processor 130 is external to the subject and so may be configuredto receive input signals from various points on the primary side of thesystem 11. As set forth in flow chart 3500, the first processor 130 maycalculate the secondary coil heat temperature by performing variouscalculations based on the primary side input signals.

Initially, in operation 3504, the system 11 determines the voltage V₁across the external resonant network 15. As mentioned, V₁ isproportional to the power supply DC voltage V_(in), and thus does nottypically change except for scaling with frequency when the systemshifts to a different subharmonic. Thus, V₁ can be derived from systemsettings and is typically known without any measurements. Inimplementations that use a full-bridge inverter, power management module140 can calculate V₁ using V_(in) and Equation (4).

In operation 3508, the system 11 calculates the coupling coefficient kbetween the external coil 1648 and the internal coil 1656. As set forthin connection with FIG. 33, the system 11 may use Equation (2) tocalculate the coupling coefficient k based on programmed values for α,β, and γ, and measured values for the power mode duty cycle DC_(on) andthe idle mode period T_(off).

In operation 3512, the system 11 estimates the current I₂ present in theinternal coil 1656 using the voltage V₁ across the external resonantnetwork 15 and the coupling coefficient k between the external coil 1648and the internal coil 1656. The system 11 may determine the current I₂present in the internal coil 1656 using the value for the voltage V₁obtained in operation 3504 and the value for the coupling coefficient kobtained in operation 3508. Specifically, the first processor 130 mayenter these measured values into Equation (3) and in so doing obtain anestimation for the current I₂.

In operation 3516, the system 11 estimates secondary coil heat fluxusing current I₂. As mentioned, heat flux in the secondary is based onthe current I₂ in the secondary coil, the known parasitic resistance ofsecondary coil, and the surface area of the secondary coil. Thus, theheat flux in the secondary can be calculated or otherwise estimatedusing the current I₂ present in the internal coil 1656 as determined inoperation 2412. Here, the first processor 130 can calculate the heatflux in the secondary using Equation (5).

In operation 3520, the system 11 estimates the secondary coiltemperature using the secondary heat flux. In one implementation, thesystem 11 may estimate temperature changes based on heat flux levelsestimations made over a certain time interval. Thus, the first processor130 may measure and record a number of heat flux calculations as setforth in operation 3516 and make temperature estimations based on theseheat flux calculations. The power management module 140 may correlatetemperature increases with sustained elevated heat flux levels.Similarly, the first processor 130 may correlate temperature decreaseswith lower heat flux levels that are maintained over time. Heat flux totemperature correlations can be based on animal studies which can beupdated on an on-going basis.

FIG. 36 is a flow chart 3600 that illustrates a method of estimating aprimary coil heat flux in accordance with embodiments discussed herein.The method illustrated by the flow chart 3600 includes operationsexecuted by the power management module 140 shown in FIG. 5. The firstprocessor 130 is external to the subject and so may be configured toreceive input signals from various points on the primary side of thesystem 11. As set forth in flow chart 3600, the first processor 130 mayestimate the primary coil heat flux by performing various calculationsbased on the primary side input signals.

Initially, in operation 3604, the system 11 calculates the current I₁that is present in the external coil 1648. An example primary current I₁2104 is illustrated in connection with the example waveform traces shownin FIG. 21. The system 11 may determine the current I₁ based onmeasurements made in the external resonant network 15 as power istransferred from the external assembly 1504 to the internal assembly1508. Specifically, the current sensor 1620 may generate an outputsignal corresponding to the magnitude of the current flowing through theexternal coil 1648, which signal is passed as input to first processor130. The first processor 130 may then sample this signal as needed todetermine magnitude of the current that is present in the external coil1648.

In operation 3612, the system 11 estimates the primary coil heat fluxusing the current I₁. As mentioned, heat flux in the primary is based onthe current I₁ in the primary coil, the known parasitic resistance ofprimary coil, and the surface area of the primary coil. Thus, the heatflux in the primary can be calculated or otherwise estimated using thecurrent I₁ present in the external coil 1648 as determined in operation3604. Here, the first processor 130 can calculate the heat flux in theprimary using Equation (5).

FIG. 37 is a flow chart 3700 that illustrates a method of estimating aprimary coil temperature in accordance with embodiments discussedherein. The method illustrated by the flow chart 3700 includesoperations executed by the power management module 140 shown in FIG. 5.The first processor 130 is external to the subject and so may beconfigured to receive input signals from various points on the primaryside of the system 11. As set forth in flow chart 3700, the firstprocessor 130 may estimate the primary coil temperature by performingvarious calculations based on the primary side input signals.

Initially, in operation 3704, the system 11 calculates the current I₁that is present in the external coil 1648. An example primary current I₁2104 is illustrated in connection with the example waveform traces shownin FIG. 21. The system 11 may determine the current I₁ based onmeasurements made in the external resonant network 15 as power istransferred from the external assembly 1504 to the internal assembly1508. Specifically, the current sensor 1620 may generate an outputsignal corresponding to the magnitude of the current flowing through theexternal coil 1648, which signal is passed as input to the powermanagement module 140. The first processor 130 may then sample thissignal as needed to determine magnitude of the current that is presentin the external coil 1648.

In operation 3712, the system 11 estimates primary coil heat flux usingcurrent I₁. As mentioned, heat flux in the primary is based on thecurrent I₁ in the primary coil, the known parasitic resistance of theprimary coil, and the surface area of the primary coil. Thus, the heatflux in the primary can be calculated or otherwise estimated using thecurrent I₁ present in the external coil 1648 as determined in operation3704. Here, the first processor 130 can calculate the heat flux in theprimary using Equation (5).

In operation 3716, the system 11 estimates the primary coil temperatureusing the primary heat flux. In one implementation, the system 11 mayestimate temperature changes based on heat flux levels estimations madeover a certain time interval. Thus, the power management module 140 maymeasure and record a number of heat flux calculations as set forth inoperation 3712 and make temperature estimations based on these heat fluxcalculations. The first processor 130 may correlate temperatureincreases with sustained elevated heat flux levels. Similarly, the firstprocessor 130 may correlate temperature decreases with lower heat fluxlevels that are maintained over time.

Generally, as described throughout the disclosure, the system mayexecute one or any number of control operations. Similarly, the systemmay provide one or any number of levels of alerts or notifications. Thealerts may discrete or continuous. A continuously increasing ordecreasing alert may indicate multiple alert levels. For example, anaudible tone or other sound may indicate multiple levels of alert byincreasing or decreasing in volume, frequency, or the like. In anotherexample, a light may indicate multiple levels of alert by increasing ordecreasing in brightness, and so on.

The technology described herein may be implemented as logical operationsand/or modules in one or more systems. The logical operations may beimplemented as a sequence of processor-implemented steps executing inone or more computer systems and as interconnected machine or circuitmodules within one or more computer systems. Likewise, the descriptionsof various component modules may be provided in terms of operationsexecuted or effected by the modules. The resulting implementation is amatter of choice, dependent on the performance requirements of theunderlying system implementing the described technology. Accordingly,the logical operations making up the embodiments of the technologydescribed herein are referred to variously as operations, steps,objects, or modules. Furthermore, it should be understood that logicaloperations may be performed in any order, unless explicitly claimedotherwise or a specific order is inherently necessitated by the claimlanguage.

In some implementations, articles of manufacture are provided ascomputer program products that cause the instantiation of operations ona computer system to implement the invention. One implementation of acomputer program product provides a non-transitory computer programstorage medium readable by a computer system and encoding a computerprogram. It should further be understood that the described technologymay be employed in special purpose devices independent of a personalcomputer.

1. A method of monitoring and controlling power transfer between aprimary and a secondary of a transcutaneous energy transfer system usedin an implantable medical device, comprising: operating thetranscutaneous energy transfer system in a first power mode, the firstpower mode being one of a plurality of scalable power modes; determiningif the transcutaneous energy transfer system is to be switched to asecond power mode, the second power mode being one of the plurality ofscalable power modes; and switching from the first power mode to thesecond power mode by controlling power transfer between the primary andsecondary.
 2. The method of claim 1, wherein the primary includes apower transmitting system including a primary coil.
 3. The method ofclaim 1, wherein the secondary includes a power receiving systemincluding a secondary coil.
 4. The method of claim 1, wherein thescalable power modes includes a set of power delivery ranges definedfrom a low power range to a high power range.
 5. The method of claim 4,wherein the set of power delivery ranges includes at least oneintermediate power delivery range between the low power range and thehigh power range.
 6. The method of claim 1, wherein determining if thetranscutaneous energy transfer system is to be switched includesdetermining if a request to complete an initial powerup sequence isreceived.
 7. The method of claim 1, wherein determining if thetranscutaneous energy transfer system is to be switched includesdetermining if a request to verify the correct secondary is received. 8.The method of claim 1, wherein determining if the transcutaneous energytransfer system is to be switched includes determining if a request forincreased or decreased power is received.
 9. The method of claim 1,wherein determining if the transcutaneous energy transfer system is tobe switched includes determining if a request to enter a fault mode isreceived.
 10. The method of claim 1, wherein determining if thetranscutaneous energy transfer system is to be switched includesdetermining if a predetermined time has elapsed since power up.
 11. Themethod of claim 1, wherein determining if the transcutaneous energytransfer system is to be switched includes determining if apredetermined time has elapsed since a fault condition was detected. 12.The method of claim 1, wherein determining if the transcutaneous energytransfer system is to be switched includes determining if apredetermined time has elapsed since a change in a coupling coefficientoccurred.
 13. The method of claim 1, wherein determining if thetranscutaneous energy transfer system is to be switched includesdetermining if a fault condition is detected.
 14. The method of claim13, wherein the fault condition includes excess current being drawn bythe secondary.
 15. The method of claim 1, wherein determining if thetranscutaneous energy transfer system is to be switched includesdetermining if a change in the coupling coefficient is detected.
 16. Themethod of claim 1, wherein determining if the transcutaneous energytransfer system is to be switched includes determining if a load changeis detected.
 17. The method of claim 16, wherein the load change isindicated in by a change in the duty cycle measured at the primary. 18.The method of claim 1, wherein controlling power transfer between theprimary and secondary includes changing the power mode by an operationof a variable transformer on the primary side.
 19. The method of claim8, wherein the variable transformer has a plurality of discrete stateseach corresponding to one of the scalable power modes.
 20. The method ofclaim 1, wherein controlling power transfer between the primary andsecondary includes changing the power mode by varying input power withsubharmonics of drive frequency.
 21. The method of claim 10, wherein theinput power has a plurality of subharmonic states each corresponding toone of the scalable power modes.
 22. The method of claim 1, whereincontrolling the power transfer between the primary and secondaryincludes changing the power mode by an operation of a variable voltageregulator on the primary side.
 23. The method of claim 12 wherein thevariable voltage regulator has a plurality of discrete states eachcorresponding to one of the scalable power modes.
 24. The method ofclaim 1, wherein controlling the power transfer between the primary andsecondary includes changing the power mode by an operation of a phaseshifted bridge controller on the primary side.
 25. The method of claim24 wherein the phase shifted bridge controller is configured for aplurality of phase shifts each corresponding to one of the scalablepower modes.
 26. A transformer for a transcutaneous energy transmissiondevice, the transformer comprising a cored transformer having a primaryside and a secondary side, the primary side configured to connect to apower supply; a variable transformer section having a first end and asecond end, the first end connected to the secondary side of the coredtransformer; and a coreless transformer having a primary side and asecondary side, the primary side connected to the second end of thevariable transformer section, the secondary side configured to beimplanted within a subject such that the skin of the subject is disposedbetween the primary and secondary sides of the coreless transformer. 27.The transformer of claim 26, wherein the variable transformer sectionfurther comprises a terminal winding configured as the primary windingof the coreless transformer; a first transformer leg having atransformer winding connected to the second side of cored transformer;and a second transformer leg having a transformer winding connected tothe second side of the cored transformer.
 28. The transformer of claim27, wherein the first transformer leg and the second transformer leg arearranged in parallel.
 29. The transformer of claim 27, wherein the firsttransformer leg includes capacitor connected in series with thetransformer winding connected to the secondary side of coredtransformer; and the second transformer leg includes capacitor connectedin series with the transformer winding connected to the secondary sideof cored transformer.
 30. The transformer of claim 27, wherein the firsttransformer leg includes a switch that, when opened, disconnects thefirst leg from the terminal winding; and the second transformer legincludes a switch that, when opened, disconnects the second leg from theterminal winding.
 31. The transformer of claim 30, wherein the switchesof the first and second transformer legs are connected to a controllerthat opens and closes the switches to switch the transcutaneous energytransmission device between at least a high power mode and a low powermode.